zig/std/mem.zig

1535 lines
51 KiB
Zig

const std = @import("std.zig");
const debug = std.debug;
const assert = debug.assert;
const math = std.math;
const builtin = @import("builtin");
const mem = @This();
const meta = std.meta;
const trait = meta.trait;
const testing = std.testing;
pub const page_size = switch (builtin.arch) {
.wasm32, .wasm64 => 64 * 1024,
else => 4 * 1024,
};
pub const Allocator = struct {
pub const Error = error{OutOfMemory};
/// Realloc is used to modify the size or alignment of an existing allocation,
/// as well as to provide the allocator with an opportunity to move an allocation
/// to a better location.
/// When the size/alignment is greater than the previous allocation, this function
/// returns `error.OutOfMemory` when the requested new allocation could not be granted.
/// When the size/alignment is less than or equal to the previous allocation,
/// this function returns `error.OutOfMemory` when the allocator decides the client
/// would be better off keeping the extra alignment/size. Clients will call
/// `shrinkFn` when they require the allocator to track a new alignment/size,
/// and so this function should only return success when the allocator considers
/// the reallocation desirable from the allocator's perspective.
/// As an example, `std.ArrayList` tracks a "capacity", and therefore can handle
/// reallocation failure, even when `new_n` <= `old_mem.len`. A `FixedBufferAllocator`
/// would always return `error.OutOfMemory` for `reallocFn` when the size/alignment
/// is less than or equal to the old allocation, because it cannot reclaim the memory,
/// and thus the `std.ArrayList` would be better off retaining its capacity.
/// When `reallocFn` returns,
/// `return_value[0..min(old_mem.len, new_byte_count)]` must be the same
/// as `old_mem` was when `reallocFn` is called. The bytes of
/// `return_value[old_mem.len..]` have undefined values.
/// The returned slice must have its pointer aligned at least to `new_alignment` bytes.
reallocFn: fn (
self: *Allocator,
/// Guaranteed to be the same as what was returned from most recent call to
/// `reallocFn` or `shrinkFn`.
/// If `old_mem.len == 0` then this is a new allocation and `new_byte_count`
/// is guaranteed to be >= 1.
old_mem: []u8,
/// If `old_mem.len == 0` then this is `undefined`, otherwise:
/// Guaranteed to be the same as what was returned from most recent call to
/// `reallocFn` or `shrinkFn`.
/// Guaranteed to be >= 1.
/// Guaranteed to be a power of 2.
old_alignment: u29,
/// If `new_byte_count` is 0 then this is a free and it is guaranteed that
/// `old_mem.len != 0`.
new_byte_count: usize,
/// Guaranteed to be >= 1.
/// Guaranteed to be a power of 2.
/// Returned slice's pointer must have this alignment.
new_alignment: u29,
) Error![]u8,
/// This function deallocates memory. It must succeed.
shrinkFn: fn (
self: *Allocator,
/// Guaranteed to be the same as what was returned from most recent call to
/// `reallocFn` or `shrinkFn`.
old_mem: []u8,
/// Guaranteed to be the same as what was returned from most recent call to
/// `reallocFn` or `shrinkFn`.
old_alignment: u29,
/// Guaranteed to be less than or equal to `old_mem.len`.
new_byte_count: usize,
/// If `new_byte_count == 0` then this is `undefined`, otherwise:
/// Guaranteed to be less than or equal to `old_alignment`.
new_alignment: u29,
) []u8,
/// Call `destroy` with the result.
/// Returns undefined memory.
pub fn create(self: *Allocator, comptime T: type) Error!*T {
if (@sizeOf(T) == 0) return &(T{});
const slice = try self.alloc(T, 1);
return &slice[0];
}
/// `ptr` should be the return value of `create`
pub fn destroy(self: *Allocator, ptr: var) void {
const T = @typeOf(ptr).Child;
if (@sizeOf(T) == 0) return;
const non_const_ptr = @intToPtr([*]u8, @ptrToInt(ptr));
const shrink_result = self.shrinkFn(self, non_const_ptr[0..@sizeOf(T)], @alignOf(T), 0, 1);
assert(shrink_result.len == 0);
}
pub fn alloc(self: *Allocator, comptime T: type, n: usize) ![]T {
return self.alignedAlloc(T, @alignOf(T), n);
}
pub fn alignedAlloc(
self: *Allocator,
comptime T: type,
comptime alignment: u29,
n: usize,
) ![]align(alignment) T {
if (n == 0) {
return ([*]align(alignment) T)(undefined)[0..0];
}
const byte_count = math.mul(usize, @sizeOf(T), n) catch return Error.OutOfMemory;
const byte_slice = try self.reallocFn(self, ([*]u8)(undefined)[0..0], undefined, byte_count, alignment);
assert(byte_slice.len == byte_count);
@memset(byte_slice.ptr, undefined, byte_slice.len);
return @bytesToSlice(T, @alignCast(alignment, byte_slice));
}
/// This function requests a new byte size for an existing allocation,
/// which can be larger, smaller, or the same size as the old memory
/// allocation.
/// This function is preferred over `shrink`, because it can fail, even
/// when shrinking. This gives the allocator a chance to perform a
/// cheap shrink operation if possible, or otherwise return OutOfMemory,
/// indicating that the caller should keep their capacity, for example
/// in `std.ArrayList.shrink`.
/// If you need guaranteed success, call `shrink`.
/// If `new_n` is 0, this is the same as `free` and it always succeeds.
pub fn realloc(self: *Allocator, old_mem: var, new_n: usize) t: {
const Slice = @typeInfo(@typeOf(old_mem)).Pointer;
break :t Error![]align(Slice.alignment) Slice.child;
} {
const old_alignment = @typeInfo(@typeOf(old_mem)).Pointer.alignment;
return self.alignedRealloc(old_mem, old_alignment, new_n);
}
/// This is the same as `realloc`, except caller may additionally request
/// a new alignment, which can be larger, smaller, or the same as the old
/// allocation.
pub fn alignedRealloc(
self: *Allocator,
old_mem: var,
comptime new_alignment: u29,
new_n: usize,
) Error![]align(new_alignment) @typeInfo(@typeOf(old_mem)).Pointer.child {
const Slice = @typeInfo(@typeOf(old_mem)).Pointer;
const T = Slice.child;
if (old_mem.len == 0) {
return self.alignedAlloc(T, new_alignment, new_n);
}
if (new_n == 0) {
self.free(old_mem);
return ([*]align(new_alignment) T)(undefined)[0..0];
}
const old_byte_slice = @sliceToBytes(old_mem);
const byte_count = math.mul(usize, @sizeOf(T), new_n) catch return Error.OutOfMemory;
const byte_slice = try self.reallocFn(self, old_byte_slice, Slice.alignment, byte_count, new_alignment);
assert(byte_slice.len == byte_count);
if (new_n > old_mem.len) {
@memset(byte_slice.ptr + old_byte_slice.len, undefined, byte_slice.len - old_byte_slice.len);
}
return @bytesToSlice(T, @alignCast(new_alignment, byte_slice));
}
/// Prefer calling realloc to shrink if you can tolerate failure, such as
/// in an ArrayList data structure with a storage capacity.
/// Shrink always succeeds, and `new_n` must be <= `old_mem.len`.
/// Returned slice has same alignment as old_mem.
/// Shrinking to 0 is the same as calling `free`.
pub fn shrink(self: *Allocator, old_mem: var, new_n: usize) t: {
const Slice = @typeInfo(@typeOf(old_mem)).Pointer;
break :t []align(Slice.alignment) Slice.child;
} {
const old_alignment = @typeInfo(@typeOf(old_mem)).Pointer.alignment;
return self.alignedShrink(old_mem, old_alignment, new_n);
}
/// This is the same as `shrink`, except caller may additionally request
/// a new alignment, which must be smaller or the same as the old
/// allocation.
pub fn alignedShrink(
self: *Allocator,
old_mem: var,
comptime new_alignment: u29,
new_n: usize,
) []align(new_alignment) @typeInfo(@typeOf(old_mem)).Pointer.child {
const Slice = @typeInfo(@typeOf(old_mem)).Pointer;
const T = Slice.child;
if (new_n == 0) {
self.free(old_mem);
return old_mem[0..0];
}
assert(new_n <= old_mem.len);
assert(new_alignment <= Slice.alignment);
// Here we skip the overflow checking on the multiplication because
// new_n <= old_mem.len and the multiplication didn't overflow for that operation.
const byte_count = @sizeOf(T) * new_n;
const old_byte_slice = @sliceToBytes(old_mem);
const byte_slice = self.shrinkFn(self, old_byte_slice, Slice.alignment, byte_count, new_alignment);
assert(byte_slice.len == byte_count);
return @bytesToSlice(T, @alignCast(new_alignment, byte_slice));
}
pub fn free(self: *Allocator, memory: var) void {
const Slice = @typeInfo(@typeOf(memory)).Pointer;
const bytes = @sliceToBytes(memory);
if (bytes.len == 0) return;
const non_const_ptr = @intToPtr([*]u8, @ptrToInt(bytes.ptr));
const shrink_result = self.shrinkFn(self, non_const_ptr[0..bytes.len], Slice.alignment, 0, 1);
assert(shrink_result.len == 0);
}
};
pub const Compare = enum {
LessThan,
Equal,
GreaterThan,
};
/// Copy all of source into dest at position 0.
/// dest.len must be >= source.len.
/// dest.ptr must be <= src.ptr.
pub fn copy(comptime T: type, dest: []T, source: []const T) void {
// TODO instead of manually doing this check for the whole array
// and turning off runtime safety, the compiler should detect loops like
// this and automatically omit safety checks for loops
@setRuntimeSafety(false);
assert(dest.len >= source.len);
for (source) |s, i|
dest[i] = s;
}
/// Copy all of source into dest at position 0.
/// dest.len must be >= source.len.
/// dest.ptr must be >= src.ptr.
pub fn copyBackwards(comptime T: type, dest: []T, source: []const T) void {
// TODO instead of manually doing this check for the whole array
// and turning off runtime safety, the compiler should detect loops like
// this and automatically omit safety checks for loops
@setRuntimeSafety(false);
assert(dest.len >= source.len);
var i = source.len;
while (i > 0) {
i -= 1;
dest[i] = source[i];
}
}
pub fn set(comptime T: type, dest: []T, value: T) void {
for (dest) |*d|
d.* = value;
}
pub fn secureZero(comptime T: type, s: []T) void {
// NOTE: We do not use a volatile slice cast here since LLVM cannot
// see that it can be replaced by a memset.
const ptr = @ptrCast([*]volatile u8, s.ptr);
const length = s.len * @sizeOf(T);
@memset(ptr, 0, length);
}
test "mem.secureZero" {
var a = [_]u8{0xfe} ** 8;
var b = [_]u8{0xfe} ** 8;
set(u8, a[0..], 0);
secureZero(u8, b[0..]);
testing.expectEqualSlices(u8, a[0..], b[0..]);
}
pub fn compare(comptime T: type, lhs: []const T, rhs: []const T) Compare {
const n = math.min(lhs.len, rhs.len);
var i: usize = 0;
while (i < n) : (i += 1) {
if (lhs[i] == rhs[i]) {
continue;
} else if (lhs[i] < rhs[i]) {
return Compare.LessThan;
} else if (lhs[i] > rhs[i]) {
return Compare.GreaterThan;
} else {
unreachable;
}
}
if (lhs.len == rhs.len) {
return Compare.Equal;
} else if (lhs.len < rhs.len) {
return Compare.LessThan;
} else if (lhs.len > rhs.len) {
return Compare.GreaterThan;
}
unreachable;
}
test "mem.compare" {
testing.expect(compare(u8, "abcd", "bee") == Compare.LessThan);
testing.expect(compare(u8, "abc", "abc") == Compare.Equal);
testing.expect(compare(u8, "abc", "abc0") == Compare.LessThan);
testing.expect(compare(u8, "", "") == Compare.Equal);
testing.expect(compare(u8, "", "a") == Compare.LessThan);
}
/// Returns true if lhs < rhs, false otherwise
pub fn lessThan(comptime T: type, lhs: []const T, rhs: []const T) bool {
var result = compare(T, lhs, rhs);
if (result == Compare.LessThan) {
return true;
} else
return false;
}
test "mem.lessThan" {
testing.expect(lessThan(u8, "abcd", "bee"));
testing.expect(!lessThan(u8, "abc", "abc"));
testing.expect(lessThan(u8, "abc", "abc0"));
testing.expect(!lessThan(u8, "", ""));
testing.expect(lessThan(u8, "", "a"));
}
/// Compares two slices and returns whether they are equal.
pub fn eql(comptime T: type, a: []const T, b: []const T) bool {
if (a.len != b.len) return false;
for (a) |item, index| {
if (b[index] != item) return false;
}
return true;
}
pub fn len(comptime T: type, ptr: [*]const T) usize {
var count: usize = 0;
while (ptr[count] != 0) : (count += 1) {}
return count;
}
pub fn toSliceConst(comptime T: type, ptr: [*]const T) []const T {
return ptr[0..len(T, ptr)];
}
pub fn toSlice(comptime T: type, ptr: [*]T) []T {
return ptr[0..len(T, ptr)];
}
/// Returns true if all elements in a slice are equal to the scalar value provided
pub fn allEqual(comptime T: type, slice: []const T, scalar: T) bool {
for (slice) |item| {
if (item != scalar) return false;
}
return true;
}
/// Copies ::m to newly allocated memory. Caller is responsible to free it.
pub fn dupe(allocator: *Allocator, comptime T: type, m: []const T) ![]T {
const new_buf = try allocator.alloc(T, m.len);
copy(T, new_buf, m);
return new_buf;
}
/// Remove values from the beginning of a slice.
pub fn trimLeft(comptime T: type, slice: []const T, values_to_strip: []const T) []const T {
var begin: usize = 0;
while (begin < slice.len and indexOfScalar(T, values_to_strip, slice[begin]) != null) : (begin += 1) {}
return slice[begin..];
}
/// Remove values from the end of a slice.
pub fn trimRight(comptime T: type, slice: []const T, values_to_strip: []const T) []const T {
var end: usize = slice.len;
while (end > 0 and indexOfScalar(T, values_to_strip, slice[end - 1]) != null) : (end -= 1) {}
return slice[0..end];
}
/// Remove values from the beginning and end of a slice.
pub fn trim(comptime T: type, slice: []const T, values_to_strip: []const T) []const T {
var begin: usize = 0;
var end: usize = slice.len;
while (begin < end and indexOfScalar(T, values_to_strip, slice[begin]) != null) : (begin += 1) {}
while (end > begin and indexOfScalar(T, values_to_strip, slice[end - 1]) != null) : (end -= 1) {}
return slice[begin..end];
}
test "mem.trim" {
testing.expectEqualSlices(u8, "foo\n ", trimLeft(u8, " foo\n ", " \n"));
testing.expectEqualSlices(u8, " foo", trimRight(u8, " foo\n ", " \n"));
testing.expectEqualSlices(u8, "foo", trim(u8, " foo\n ", " \n"));
testing.expectEqualSlices(u8, "foo", trim(u8, "foo", " \n"));
}
/// Linear search for the index of a scalar value inside a slice.
pub fn indexOfScalar(comptime T: type, slice: []const T, value: T) ?usize {
return indexOfScalarPos(T, slice, 0, value);
}
/// Linear search for the last index of a scalar value inside a slice.
pub fn lastIndexOfScalar(comptime T: type, slice: []const T, value: T) ?usize {
var i: usize = slice.len;
while (i != 0) {
i -= 1;
if (slice[i] == value) return i;
}
return null;
}
pub fn indexOfScalarPos(comptime T: type, slice: []const T, start_index: usize, value: T) ?usize {
var i: usize = start_index;
while (i < slice.len) : (i += 1) {
if (slice[i] == value) return i;
}
return null;
}
pub fn indexOfAny(comptime T: type, slice: []const T, values: []const T) ?usize {
return indexOfAnyPos(T, slice, 0, values);
}
pub fn lastIndexOfAny(comptime T: type, slice: []const T, values: []const T) ?usize {
var i: usize = slice.len;
while (i != 0) {
i -= 1;
for (values) |value| {
if (slice[i] == value) return i;
}
}
return null;
}
pub fn indexOfAnyPos(comptime T: type, slice: []const T, start_index: usize, values: []const T) ?usize {
var i: usize = start_index;
while (i < slice.len) : (i += 1) {
for (values) |value| {
if (slice[i] == value) return i;
}
}
return null;
}
pub fn indexOf(comptime T: type, haystack: []const T, needle: []const T) ?usize {
return indexOfPos(T, haystack, 0, needle);
}
/// Find the index in a slice of a sub-slice, searching from the end backwards.
/// To start looking at a different index, slice the haystack first.
/// TODO is there even a better algorithm for this?
pub fn lastIndexOf(comptime T: type, haystack: []const T, needle: []const T) ?usize {
if (needle.len > haystack.len) return null;
var i: usize = haystack.len - needle.len;
while (true) : (i -= 1) {
if (mem.eql(T, haystack[i .. i + needle.len], needle)) return i;
if (i == 0) return null;
}
}
// TODO boyer-moore algorithm
pub fn indexOfPos(comptime T: type, haystack: []const T, start_index: usize, needle: []const T) ?usize {
if (needle.len > haystack.len) return null;
var i: usize = start_index;
const end = haystack.len - needle.len;
while (i <= end) : (i += 1) {
if (eql(T, haystack[i .. i + needle.len], needle)) return i;
}
return null;
}
test "mem.indexOf" {
testing.expect(indexOf(u8, "one two three four", "four").? == 14);
testing.expect(lastIndexOf(u8, "one two three two four", "two").? == 14);
testing.expect(indexOf(u8, "one two three four", "gour") == null);
testing.expect(lastIndexOf(u8, "one two three four", "gour") == null);
testing.expect(indexOf(u8, "foo", "foo").? == 0);
testing.expect(lastIndexOf(u8, "foo", "foo").? == 0);
testing.expect(indexOf(u8, "foo", "fool") == null);
testing.expect(lastIndexOf(u8, "foo", "lfoo") == null);
testing.expect(lastIndexOf(u8, "foo", "fool") == null);
testing.expect(indexOf(u8, "foo foo", "foo").? == 0);
testing.expect(lastIndexOf(u8, "foo foo", "foo").? == 4);
testing.expect(lastIndexOfAny(u8, "boo, cat", "abo").? == 6);
testing.expect(lastIndexOfScalar(u8, "boo", 'o').? == 2);
}
/// Reads an integer from memory with size equal to bytes.len.
/// T specifies the return type, which must be large enough to store
/// the result.
pub fn readVarInt(comptime ReturnType: type, bytes: []const u8, endian: builtin.Endian) ReturnType {
var result: ReturnType = 0;
switch (endian) {
builtin.Endian.Big => {
for (bytes) |b| {
result = (result << 8) | b;
}
},
builtin.Endian.Little => {
const ShiftType = math.Log2Int(ReturnType);
for (bytes) |b, index| {
result = result | (ReturnType(b) << @intCast(ShiftType, index * 8));
}
},
}
return result;
}
/// Reads an integer from memory with bit count specified by T.
/// The bit count of T must be evenly divisible by 8.
/// This function cannot fail and cannot cause undefined behavior.
/// Assumes the endianness of memory is native. This means the function can
/// simply pointer cast memory.
pub fn readIntNative(comptime T: type, bytes: *const [@divExact(T.bit_count, 8)]u8) T {
return @ptrCast(*align(1) const T, bytes).*;
}
/// Reads an integer from memory with bit count specified by T.
/// The bit count of T must be evenly divisible by 8.
/// This function cannot fail and cannot cause undefined behavior.
/// Assumes the endianness of memory is foreign, so it must byte-swap.
pub fn readIntForeign(comptime T: type, bytes: *const [@divExact(T.bit_count, 8)]u8) T {
return @byteSwap(T, readIntNative(T, bytes));
}
pub const readIntLittle = switch (builtin.endian) {
builtin.Endian.Little => readIntNative,
builtin.Endian.Big => readIntForeign,
};
pub const readIntBig = switch (builtin.endian) {
builtin.Endian.Little => readIntForeign,
builtin.Endian.Big => readIntNative,
};
/// Asserts that bytes.len >= T.bit_count / 8. Reads the integer starting from index 0
/// and ignores extra bytes.
/// The bit count of T must be evenly divisible by 8.
/// Assumes the endianness of memory is native. This means the function can
/// simply pointer cast memory.
pub fn readIntSliceNative(comptime T: type, bytes: []const u8) T {
const n = @divExact(T.bit_count, 8);
assert(bytes.len >= n);
// TODO https://github.com/ziglang/zig/issues/863
return readIntNative(T, @ptrCast(*const [n]u8, bytes.ptr));
}
/// Asserts that bytes.len >= T.bit_count / 8. Reads the integer starting from index 0
/// and ignores extra bytes.
/// The bit count of T must be evenly divisible by 8.
/// Assumes the endianness of memory is foreign, so it must byte-swap.
pub fn readIntSliceForeign(comptime T: type, bytes: []const u8) T {
return @byteSwap(T, readIntSliceNative(T, bytes));
}
pub const readIntSliceLittle = switch (builtin.endian) {
builtin.Endian.Little => readIntSliceNative,
builtin.Endian.Big => readIntSliceForeign,
};
pub const readIntSliceBig = switch (builtin.endian) {
builtin.Endian.Little => readIntSliceForeign,
builtin.Endian.Big => readIntSliceNative,
};
/// Reads an integer from memory with bit count specified by T.
/// The bit count of T must be evenly divisible by 8.
/// This function cannot fail and cannot cause undefined behavior.
pub fn readInt(comptime T: type, bytes: *const [@divExact(T.bit_count, 8)]u8, endian: builtin.Endian) T {
if (endian == builtin.endian) {
return readIntNative(T, bytes);
} else {
return readIntForeign(T, bytes);
}
}
/// Asserts that bytes.len >= T.bit_count / 8. Reads the integer starting from index 0
/// and ignores extra bytes.
/// The bit count of T must be evenly divisible by 8.
pub fn readIntSlice(comptime T: type, bytes: []const u8, endian: builtin.Endian) T {
const n = @divExact(T.bit_count, 8);
assert(bytes.len >= n);
// TODO https://github.com/ziglang/zig/issues/863
return readInt(T, @ptrCast(*const [n]u8, bytes.ptr), endian);
}
test "comptime read/write int" {
comptime {
var bytes: [2]u8 = undefined;
writeIntLittle(u16, &bytes, 0x1234);
const result = readIntBig(u16, &bytes);
testing.expect(result == 0x3412);
}
comptime {
var bytes: [2]u8 = undefined;
writeIntBig(u16, &bytes, 0x1234);
const result = readIntLittle(u16, &bytes);
testing.expect(result == 0x3412);
}
}
test "readIntBig and readIntLittle" {
testing.expect(readIntSliceBig(u0, [_]u8{}) == 0x0);
testing.expect(readIntSliceLittle(u0, [_]u8{}) == 0x0);
testing.expect(readIntSliceBig(u8, [_]u8{0x32}) == 0x32);
testing.expect(readIntSliceLittle(u8, [_]u8{0x12}) == 0x12);
testing.expect(readIntSliceBig(u16, [_]u8{ 0x12, 0x34 }) == 0x1234);
testing.expect(readIntSliceLittle(u16, [_]u8{ 0x12, 0x34 }) == 0x3412);
testing.expect(readIntSliceBig(u72, [_]u8{ 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0, 0x24 }) == 0x123456789abcdef024);
testing.expect(readIntSliceLittle(u72, [_]u8{ 0xec, 0x10, 0x32, 0x54, 0x76, 0x98, 0xba, 0xdc, 0xfe }) == 0xfedcba9876543210ec);
testing.expect(readIntSliceBig(i8, [_]u8{0xff}) == -1);
testing.expect(readIntSliceLittle(i8, [_]u8{0xfe}) == -2);
testing.expect(readIntSliceBig(i16, [_]u8{ 0xff, 0xfd }) == -3);
testing.expect(readIntSliceLittle(i16, [_]u8{ 0xfc, 0xff }) == -4);
}
/// Writes an integer to memory, storing it in twos-complement.
/// This function always succeeds, has defined behavior for all inputs, and
/// accepts any integer bit width.
/// This function stores in native endian, which means it is implemented as a simple
/// memory store.
pub fn writeIntNative(comptime T: type, buf: *[(T.bit_count + 7) / 8]u8, value: T) void {
@ptrCast(*align(1) T, buf).* = value;
}
/// Writes an integer to memory, storing it in twos-complement.
/// This function always succeeds, has defined behavior for all inputs, but
/// the integer bit width must be divisible by 8.
/// This function stores in foreign endian, which means it does a @byteSwap first.
pub fn writeIntForeign(comptime T: type, buf: *[@divExact(T.bit_count, 8)]u8, value: T) void {
writeIntNative(T, buf, @byteSwap(T, value));
}
pub const writeIntLittle = switch (builtin.endian) {
builtin.Endian.Little => writeIntNative,
builtin.Endian.Big => writeIntForeign,
};
pub const writeIntBig = switch (builtin.endian) {
builtin.Endian.Little => writeIntForeign,
builtin.Endian.Big => writeIntNative,
};
/// Writes an integer to memory, storing it in twos-complement.
/// This function always succeeds, has defined behavior for all inputs, but
/// the integer bit width must be divisible by 8.
pub fn writeInt(comptime T: type, buffer: *[@divExact(T.bit_count, 8)]u8, value: T, endian: builtin.Endian) void {
if (endian == builtin.endian) {
return writeIntNative(T, buffer, value);
} else {
return writeIntForeign(T, buffer, value);
}
}
/// Writes a twos-complement little-endian integer to memory.
/// Asserts that buf.len >= T.bit_count / 8.
/// The bit count of T must be divisible by 8.
/// Any extra bytes in buffer after writing the integer are set to zero. To
/// avoid the branch to check for extra buffer bytes, use writeIntLittle
/// instead.
pub fn writeIntSliceLittle(comptime T: type, buffer: []u8, value: T) void {
assert(buffer.len >= @divExact(T.bit_count, 8));
// TODO I want to call writeIntLittle here but comptime eval facilities aren't good enough
const uint = @IntType(false, T.bit_count);
var bits = @truncate(uint, value);
for (buffer) |*b| {
b.* = @truncate(u8, bits);
bits >>= 8;
}
}
/// Writes a twos-complement big-endian integer to memory.
/// Asserts that buffer.len >= T.bit_count / 8.
/// The bit count of T must be divisible by 8.
/// Any extra bytes in buffer before writing the integer are set to zero. To
/// avoid the branch to check for extra buffer bytes, use writeIntBig instead.
pub fn writeIntSliceBig(comptime T: type, buffer: []u8, value: T) void {
assert(buffer.len >= @divExact(T.bit_count, 8));
// TODO I want to call writeIntBig here but comptime eval facilities aren't good enough
const uint = @IntType(false, T.bit_count);
var bits = @truncate(uint, value);
var index: usize = buffer.len;
while (index != 0) {
index -= 1;
buffer[index] = @truncate(u8, bits);
bits >>= 8;
}
}
pub const writeIntSliceNative = switch (builtin.endian) {
builtin.Endian.Little => writeIntSliceLittle,
builtin.Endian.Big => writeIntSliceBig,
};
pub const writeIntSliceForeign = switch (builtin.endian) {
builtin.Endian.Little => writeIntSliceBig,
builtin.Endian.Big => writeIntSliceLittle,
};
/// Writes a twos-complement integer to memory, with the specified endianness.
/// Asserts that buf.len >= T.bit_count / 8.
/// The bit count of T must be evenly divisible by 8.
/// Any extra bytes in buffer not part of the integer are set to zero, with
/// respect to endianness. To avoid the branch to check for extra buffer bytes,
/// use writeInt instead.
pub fn writeIntSlice(comptime T: type, buffer: []u8, value: T, endian: builtin.Endian) void {
comptime assert(T.bit_count % 8 == 0);
switch (endian) {
builtin.Endian.Little => return writeIntSliceLittle(T, buffer, value),
builtin.Endian.Big => return writeIntSliceBig(T, buffer, value),
}
}
test "writeIntBig and writeIntLittle" {
var buf0: [0]u8 = undefined;
var buf1: [1]u8 = undefined;
var buf2: [2]u8 = undefined;
var buf9: [9]u8 = undefined;
writeIntBig(u0, &buf0, 0x0);
testing.expect(eql_slice_u8(buf0[0..], [_]u8{}));
writeIntLittle(u0, &buf0, 0x0);
testing.expect(eql_slice_u8(buf0[0..], [_]u8{}));
writeIntBig(u8, &buf1, 0x12);
testing.expect(eql_slice_u8(buf1[0..], [_]u8{0x12}));
writeIntLittle(u8, &buf1, 0x34);
testing.expect(eql_slice_u8(buf1[0..], [_]u8{0x34}));
writeIntBig(u16, &buf2, 0x1234);
testing.expect(eql_slice_u8(buf2[0..], [_]u8{ 0x12, 0x34 }));
writeIntLittle(u16, &buf2, 0x5678);
testing.expect(eql_slice_u8(buf2[0..], [_]u8{ 0x78, 0x56 }));
writeIntBig(u72, &buf9, 0x123456789abcdef024);
testing.expect(eql_slice_u8(buf9[0..], [_]u8{ 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0, 0x24 }));
writeIntLittle(u72, &buf9, 0xfedcba9876543210ec);
testing.expect(eql_slice_u8(buf9[0..], [_]u8{ 0xec, 0x10, 0x32, 0x54, 0x76, 0x98, 0xba, 0xdc, 0xfe }));
writeIntBig(i8, &buf1, -1);
testing.expect(eql_slice_u8(buf1[0..], [_]u8{0xff}));
writeIntLittle(i8, &buf1, -2);
testing.expect(eql_slice_u8(buf1[0..], [_]u8{0xfe}));
writeIntBig(i16, &buf2, -3);
testing.expect(eql_slice_u8(buf2[0..], [_]u8{ 0xff, 0xfd }));
writeIntLittle(i16, &buf2, -4);
testing.expect(eql_slice_u8(buf2[0..], [_]u8{ 0xfc, 0xff }));
}
pub fn hash_slice_u8(k: []const u8) u32 {
// FNV 32-bit hash
var h: u32 = 2166136261;
for (k) |b| {
h = (h ^ b) *% 16777619;
}
return h;
}
pub fn eql_slice_u8(a: []const u8, b: []const u8) bool {
return eql(u8, a, b);
}
/// Returns an iterator that iterates over the slices of `buffer` that are not
/// any of the bytes in `delimiter_bytes`.
/// tokenize(" abc def ghi ", " ")
/// Will return slices for "abc", "def", "ghi", null, in that order.
/// If `buffer` is empty, the iterator will return null.
/// If `delimiter_bytes` does not exist in buffer,
/// the iterator will return `buffer`, null, in that order.
/// See also the related function `separate`.
pub fn tokenize(buffer: []const u8, delimiter_bytes: []const u8) TokenIterator {
return TokenIterator{
.index = 0,
.buffer = buffer,
.delimiter_bytes = delimiter_bytes,
};
}
test "mem.tokenize" {
var it = tokenize(" abc def ghi ", " ");
testing.expect(eql(u8, it.next().?, "abc"));
testing.expect(eql(u8, it.next().?, "def"));
testing.expect(eql(u8, it.next().?, "ghi"));
testing.expect(it.next() == null);
it = tokenize("..\\bob", "\\");
testing.expect(eql(u8, it.next().?, ".."));
testing.expect(eql(u8, "..", "..\\bob"[0..it.index]));
testing.expect(eql(u8, it.next().?, "bob"));
testing.expect(it.next() == null);
it = tokenize("//a/b", "/");
testing.expect(eql(u8, it.next().?, "a"));
testing.expect(eql(u8, it.next().?, "b"));
testing.expect(eql(u8, "//a/b", "//a/b"[0..it.index]));
testing.expect(it.next() == null);
it = tokenize("|", "|");
testing.expect(it.next() == null);
it = tokenize("", "|");
testing.expect(it.next() == null);
it = tokenize("hello", "");
testing.expect(eql(u8, it.next().?, "hello"));
testing.expect(it.next() == null);
it = tokenize("hello", " ");
testing.expect(eql(u8, it.next().?, "hello"));
testing.expect(it.next() == null);
}
test "mem.tokenize (multibyte)" {
var it = tokenize("a|b,c/d e", " /,|");
testing.expect(eql(u8, it.next().?, "a"));
testing.expect(eql(u8, it.next().?, "b"));
testing.expect(eql(u8, it.next().?, "c"));
testing.expect(eql(u8, it.next().?, "d"));
testing.expect(eql(u8, it.next().?, "e"));
testing.expect(it.next() == null);
}
/// Returns an iterator that iterates over the slices of `buffer` that
/// are separated by bytes in `delimiter`.
/// separate("abc|def||ghi", "|")
/// will return slices for "abc", "def", "", "ghi", null, in that order.
/// If `delimiter` does not exist in buffer,
/// the iterator will return `buffer`, null, in that order.
/// The delimiter length must not be zero.
/// See also the related function `tokenize`.
/// It is planned to rename this function to `split` before 1.0.0, like this:
/// pub fn split(buffer: []const u8, delimiter: []const u8) SplitIterator {
pub fn separate(buffer: []const u8, delimiter: []const u8) SplitIterator {
assert(delimiter.len != 0);
return SplitIterator{
.index = 0,
.buffer = buffer,
.delimiter = delimiter,
};
}
test "mem.separate" {
var it = separate("abc|def||ghi", "|");
testing.expect(eql(u8, it.next().?, "abc"));
testing.expect(eql(u8, it.next().?, "def"));
testing.expect(eql(u8, it.next().?, ""));
testing.expect(eql(u8, it.next().?, "ghi"));
testing.expect(it.next() == null);
it = separate("", "|");
testing.expect(eql(u8, it.next().?, ""));
testing.expect(it.next() == null);
it = separate("|", "|");
testing.expect(eql(u8, it.next().?, ""));
testing.expect(eql(u8, it.next().?, ""));
testing.expect(it.next() == null);
it = separate("hello", " ");
testing.expect(eql(u8, it.next().?, "hello"));
testing.expect(it.next() == null);
}
test "mem.separate (multibyte)" {
var it = separate("a, b ,, c, d, e", ", ");
testing.expect(eql(u8, it.next().?, "a"));
testing.expect(eql(u8, it.next().?, "b ,"));
testing.expect(eql(u8, it.next().?, "c"));
testing.expect(eql(u8, it.next().?, "d"));
testing.expect(eql(u8, it.next().?, "e"));
testing.expect(it.next() == null);
}
pub fn startsWith(comptime T: type, haystack: []const T, needle: []const T) bool {
return if (needle.len > haystack.len) false else eql(T, haystack[0..needle.len], needle);
}
test "mem.startsWith" {
testing.expect(startsWith(u8, "Bob", "Bo"));
testing.expect(!startsWith(u8, "Needle in haystack", "haystack"));
}
pub fn endsWith(comptime T: type, haystack: []const T, needle: []const T) bool {
return if (needle.len > haystack.len) false else eql(T, haystack[haystack.len - needle.len ..], needle);
}
test "mem.endsWith" {
testing.expect(endsWith(u8, "Needle in haystack", "haystack"));
testing.expect(!endsWith(u8, "Bob", "Bo"));
}
pub const TokenIterator = struct {
buffer: []const u8,
delimiter_bytes: []const u8,
index: usize,
/// Returns a slice of the next token, or null if tokenization is complete.
pub fn next(self: *TokenIterator) ?[]const u8 {
// move to beginning of token
while (self.index < self.buffer.len and self.isSplitByte(self.buffer[self.index])) : (self.index += 1) {}
const start = self.index;
if (start == self.buffer.len) {
return null;
}
// move to end of token
while (self.index < self.buffer.len and !self.isSplitByte(self.buffer[self.index])) : (self.index += 1) {}
const end = self.index;
return self.buffer[start..end];
}
/// Returns a slice of the remaining bytes. Does not affect iterator state.
pub fn rest(self: TokenIterator) []const u8 {
// move to beginning of token
var index: usize = self.index;
while (index < self.buffer.len and self.isSplitByte(self.buffer[index])) : (index += 1) {}
return self.buffer[index..];
}
fn isSplitByte(self: TokenIterator, byte: u8) bool {
for (self.delimiter_bytes) |delimiter_byte| {
if (byte == delimiter_byte) {
return true;
}
}
return false;
}
};
pub const SplitIterator = struct {
buffer: []const u8,
index: ?usize,
delimiter: []const u8,
/// Returns a slice of the next field, or null if splitting is complete.
pub fn next(self: *SplitIterator) ?[]const u8 {
const start = self.index orelse return null;
const end = if (indexOfPos(u8, self.buffer, start, self.delimiter)) |delim_start| blk: {
self.index = delim_start + self.delimiter.len;
break :blk delim_start;
} else blk: {
self.index = null;
break :blk self.buffer.len;
};
return self.buffer[start..end];
}
/// Returns a slice of the remaining bytes. Does not affect iterator state.
pub fn rest(self: SplitIterator) []const u8 {
const end = self.buffer.len;
const start = self.index orelse end;
return self.buffer[start..end];
}
};
/// Naively combines a series of slices with a separator.
/// Allocates memory for the result, which must be freed by the caller.
pub fn join(allocator: *Allocator, separator: []const u8, slices: []const []const u8) ![]u8 {
if (slices.len == 0) return (([*]u8)(undefined))[0..0];
const total_len = blk: {
var sum: usize = separator.len * (slices.len - 1);
for (slices) |slice|
sum += slice.len;
break :blk sum;
};
const buf = try allocator.alloc(u8, total_len);
errdefer allocator.free(buf);
copy(u8, buf, slices[0]);
var buf_index: usize = slices[0].len;
for (slices[1..]) |slice| {
copy(u8, buf[buf_index..], separator);
buf_index += separator.len;
copy(u8, buf[buf_index..], slice);
buf_index += slice.len;
}
// No need for shrink since buf is exactly the correct size.
return buf;
}
test "mem.join" {
var buf: [1024]u8 = undefined;
const a = &std.heap.FixedBufferAllocator.init(&buf).allocator;
testing.expect(eql(u8, try join(a, ",", [_][]const u8{ "a", "b", "c" }), "a,b,c"));
testing.expect(eql(u8, try join(a, ",", [_][]const u8{"a"}), "a"));
testing.expect(eql(u8, try join(a, ",", [_][]const u8{ "a", "", "b", "", "c" }), "a,,b,,c"));
}
/// Copies each T from slices into a new slice that exactly holds all the elements.
pub fn concat(allocator: *Allocator, comptime T: type, slices: []const []const T) ![]T {
if (slices.len == 0) return (([*]T)(undefined))[0..0];
const total_len = blk: {
var sum: usize = 0;
for (slices) |slice| {
sum += slice.len;
}
break :blk sum;
};
const buf = try allocator.alloc(T, total_len);
errdefer allocator.free(buf);
var buf_index: usize = 0;
for (slices) |slice| {
copy(T, buf[buf_index..], slice);
buf_index += slice.len;
}
// No need for shrink since buf is exactly the correct size.
return buf;
}
test "concat" {
var buf: [1024]u8 = undefined;
const a = &std.heap.FixedBufferAllocator.init(&buf).allocator;
testing.expect(eql(u8, try concat(a, u8, [_][]const u8{ "abc", "def", "ghi" }), "abcdefghi"));
testing.expect(eql(u32, try concat(a, u32, [_][]const u32{
[_]u32{ 0, 1 },
[_]u32{ 2, 3, 4 },
[_]u32{},
[_]u32{5},
}), [_]u32{ 0, 1, 2, 3, 4, 5 }));
}
test "testStringEquality" {
testing.expect(eql(u8, "abcd", "abcd"));
testing.expect(!eql(u8, "abcdef", "abZdef"));
testing.expect(!eql(u8, "abcdefg", "abcdef"));
}
test "testReadInt" {
testReadIntImpl();
comptime testReadIntImpl();
}
fn testReadIntImpl() void {
{
const bytes = [_]u8{
0x12,
0x34,
0x56,
0x78,
};
testing.expect(readInt(u32, &bytes, builtin.Endian.Big) == 0x12345678);
testing.expect(readIntBig(u32, &bytes) == 0x12345678);
testing.expect(readIntBig(i32, &bytes) == 0x12345678);
testing.expect(readInt(u32, &bytes, builtin.Endian.Little) == 0x78563412);
testing.expect(readIntLittle(u32, &bytes) == 0x78563412);
testing.expect(readIntLittle(i32, &bytes) == 0x78563412);
}
{
const buf = [_]u8{
0x00,
0x00,
0x12,
0x34,
};
const answer = readInt(u32, &buf, builtin.Endian.Big);
testing.expect(answer == 0x00001234);
}
{
const buf = [_]u8{
0x12,
0x34,
0x00,
0x00,
};
const answer = readInt(u32, &buf, builtin.Endian.Little);
testing.expect(answer == 0x00003412);
}
{
const bytes = [_]u8{
0xff,
0xfe,
};
testing.expect(readIntBig(u16, &bytes) == 0xfffe);
testing.expect(readIntBig(i16, &bytes) == -0x0002);
testing.expect(readIntLittle(u16, &bytes) == 0xfeff);
testing.expect(readIntLittle(i16, &bytes) == -0x0101);
}
}
test "writeIntSlice" {
testWriteIntImpl();
comptime testWriteIntImpl();
}
fn testWriteIntImpl() void {
var bytes: [8]u8 = undefined;
writeIntSlice(u0, bytes[0..], 0, builtin.Endian.Big);
testing.expect(eql(u8, bytes, [_]u8{
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
}));
writeIntSlice(u0, bytes[0..], 0, builtin.Endian.Little);
testing.expect(eql(u8, bytes, [_]u8{
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
}));
writeIntSlice(u64, bytes[0..], 0x12345678CAFEBABE, builtin.Endian.Big);
testing.expect(eql(u8, bytes, [_]u8{
0x12,
0x34,
0x56,
0x78,
0xCA,
0xFE,
0xBA,
0xBE,
}));
writeIntSlice(u64, bytes[0..], 0xBEBAFECA78563412, builtin.Endian.Little);
testing.expect(eql(u8, bytes, [_]u8{
0x12,
0x34,
0x56,
0x78,
0xCA,
0xFE,
0xBA,
0xBE,
}));
writeIntSlice(u32, bytes[0..], 0x12345678, builtin.Endian.Big);
testing.expect(eql(u8, bytes, [_]u8{
0x00,
0x00,
0x00,
0x00,
0x12,
0x34,
0x56,
0x78,
}));
writeIntSlice(u32, bytes[0..], 0x78563412, builtin.Endian.Little);
testing.expect(eql(u8, bytes, [_]u8{
0x12,
0x34,
0x56,
0x78,
0x00,
0x00,
0x00,
0x00,
}));
writeIntSlice(u16, bytes[0..], 0x1234, builtin.Endian.Big);
testing.expect(eql(u8, bytes, [_]u8{
0x00,
0x00,
0x00,
0x00,
0x00,
0x00,
0x12,
0x34,
}));
writeIntSlice(u16, bytes[0..], 0x1234, builtin.Endian.Little);
testing.expect(eql(u8, bytes, [_]u8{
0x34,
0x12,
0x00,
0x00,
0x00,
0x00,
0x00,
0x00,
}));
}
pub fn min(comptime T: type, slice: []const T) T {
var best = slice[0];
for (slice[1..]) |item| {
best = math.min(best, item);
}
return best;
}
test "mem.min" {
testing.expect(min(u8, "abcdefg") == 'a');
}
pub fn max(comptime T: type, slice: []const T) T {
var best = slice[0];
for (slice[1..]) |item| {
best = math.max(best, item);
}
return best;
}
test "mem.max" {
testing.expect(max(u8, "abcdefg") == 'g');
}
pub fn swap(comptime T: type, a: *T, b: *T) void {
const tmp = a.*;
a.* = b.*;
b.* = tmp;
}
/// In-place order reversal of a slice
pub fn reverse(comptime T: type, items: []T) void {
var i: usize = 0;
const end = items.len / 2;
while (i < end) : (i += 1) {
swap(T, &items[i], &items[items.len - i - 1]);
}
}
test "reverse" {
var arr = [_]i32{
5,
3,
1,
2,
4,
};
reverse(i32, arr[0..]);
testing.expect(eql(i32, arr, [_]i32{
4,
2,
1,
3,
5,
}));
}
/// In-place rotation of the values in an array ([0 1 2 3] becomes [1 2 3 0] if we rotate by 1)
/// Assumes 0 <= amount <= items.len
pub fn rotate(comptime T: type, items: []T, amount: usize) void {
reverse(T, items[0..amount]);
reverse(T, items[amount..]);
reverse(T, items);
}
test "rotate" {
var arr = [_]i32{
5,
3,
1,
2,
4,
};
rotate(i32, arr[0..], 2);
testing.expect(eql(i32, arr, [_]i32{
1,
2,
4,
5,
3,
}));
}
/// Converts a little-endian integer to host endianness.
pub fn littleToNative(comptime T: type, x: T) T {
return switch (builtin.endian) {
builtin.Endian.Little => x,
builtin.Endian.Big => @byteSwap(T, x),
};
}
/// Converts a big-endian integer to host endianness.
pub fn bigToNative(comptime T: type, x: T) T {
return switch (builtin.endian) {
builtin.Endian.Little => @byteSwap(T, x),
builtin.Endian.Big => x,
};
}
/// Converts an integer from specified endianness to host endianness.
pub fn toNative(comptime T: type, x: T, endianness_of_x: builtin.Endian) T {
return switch (endianness_of_x) {
builtin.Endian.Little => littleToNative(T, x),
builtin.Endian.Big => bigToNative(T, x),
};
}
/// Converts an integer which has host endianness to the desired endianness.
pub fn nativeTo(comptime T: type, x: T, desired_endianness: builtin.Endian) T {
return switch (desired_endianness) {
builtin.Endian.Little => nativeToLittle(T, x),
builtin.Endian.Big => nativeToBig(T, x),
};
}
/// Converts an integer which has host endianness to little endian.
pub fn nativeToLittle(comptime T: type, x: T) T {
return switch (builtin.endian) {
builtin.Endian.Little => x,
builtin.Endian.Big => @byteSwap(T, x),
};
}
/// Converts an integer which has host endianness to big endian.
pub fn nativeToBig(comptime T: type, x: T) T {
return switch (builtin.endian) {
builtin.Endian.Little => @byteSwap(T, x),
builtin.Endian.Big => x,
};
}
fn AsBytesReturnType(comptime P: type) type {
if (comptime !trait.isSingleItemPtr(P))
@compileError("expected single item " ++ "pointer, passed " ++ @typeName(P));
const size = usize(@sizeOf(meta.Child(P)));
const alignment = comptime meta.alignment(P);
if (comptime trait.isConstPtr(P))
return *align(alignment) const [size]u8;
return *align(alignment) [size]u8;
}
///Given a pointer to a single item, returns a slice of the underlying bytes, preserving constness.
pub fn asBytes(ptr: var) AsBytesReturnType(@typeOf(ptr)) {
const P = @typeOf(ptr);
return @ptrCast(AsBytesReturnType(P), ptr);
}
test "asBytes" {
const deadbeef = u32(0xDEADBEEF);
const deadbeef_bytes = switch (builtin.endian) {
builtin.Endian.Big => "\xDE\xAD\xBE\xEF",
builtin.Endian.Little => "\xEF\xBE\xAD\xDE",
};
testing.expect(eql(u8, asBytes(&deadbeef), deadbeef_bytes));
var codeface = u32(0xC0DEFACE);
for (asBytes(&codeface).*) |*b|
b.* = 0;
testing.expect(codeface == 0);
const S = packed struct {
a: u8,
b: u8,
c: u8,
d: u8,
};
const inst = S{
.a = 0xBE,
.b = 0xEF,
.c = 0xDE,
.d = 0xA1,
};
testing.expect(eql(u8, asBytes(&inst), "\xBE\xEF\xDE\xA1"));
}
///Given any value, returns a copy of its bytes in an array.
pub fn toBytes(value: var) [@sizeOf(@typeOf(value))]u8 {
return asBytes(&value).*;
}
test "toBytes" {
var my_bytes = toBytes(u32(0x12345678));
switch (builtin.endian) {
builtin.Endian.Big => testing.expect(eql(u8, my_bytes, "\x12\x34\x56\x78")),
builtin.Endian.Little => testing.expect(eql(u8, my_bytes, "\x78\x56\x34\x12")),
}
my_bytes[0] = '\x99';
switch (builtin.endian) {
builtin.Endian.Big => testing.expect(eql(u8, my_bytes, "\x99\x34\x56\x78")),
builtin.Endian.Little => testing.expect(eql(u8, my_bytes, "\x99\x56\x34\x12")),
}
}
fn BytesAsValueReturnType(comptime T: type, comptime B: type) type {
const size = usize(@sizeOf(T));
if (comptime !trait.is(builtin.TypeId.Pointer)(B) or meta.Child(B) != [size]u8) {
@compileError("expected *[N]u8 " ++ ", passed " ++ @typeName(B));
}
const alignment = comptime meta.alignment(B);
return if (comptime trait.isConstPtr(B)) *align(alignment) const T else *align(alignment) T;
}
///Given a pointer to an array of bytes, returns a pointer to a value of the specified type
/// backed by those bytes, preserving constness.
pub fn bytesAsValue(comptime T: type, bytes: var) BytesAsValueReturnType(T, @typeOf(bytes)) {
return @ptrCast(BytesAsValueReturnType(T, @typeOf(bytes)), bytes);
}
test "bytesAsValue" {
const deadbeef = u32(0xDEADBEEF);
const deadbeef_bytes = switch (builtin.endian) {
builtin.Endian.Big => "\xDE\xAD\xBE\xEF",
builtin.Endian.Little => "\xEF\xBE\xAD\xDE",
};
testing.expect(deadbeef == bytesAsValue(u32, &deadbeef_bytes).*);
var codeface_bytes = switch (builtin.endian) {
builtin.Endian.Big => "\xC0\xDE\xFA\xCE",
builtin.Endian.Little => "\xCE\xFA\xDE\xC0",
};
var codeface = bytesAsValue(u32, &codeface_bytes);
testing.expect(codeface.* == 0xC0DEFACE);
codeface.* = 0;
for (codeface_bytes) |b|
testing.expect(b == 0);
const S = packed struct {
a: u8,
b: u8,
c: u8,
d: u8,
};
const inst = S{
.a = 0xBE,
.b = 0xEF,
.c = 0xDE,
.d = 0xA1,
};
const inst_bytes = "\xBE\xEF\xDE\xA1";
const inst2 = bytesAsValue(S, &inst_bytes);
testing.expect(meta.eql(inst, inst2.*));
}
///Given a pointer to an array of bytes, returns a value of the specified type backed by a
/// copy of those bytes.
pub fn bytesToValue(comptime T: type, bytes: var) T {
return bytesAsValue(T, &bytes).*;
}
test "bytesToValue" {
const deadbeef_bytes = switch (builtin.endian) {
builtin.Endian.Big => "\xDE\xAD\xBE\xEF",
builtin.Endian.Little => "\xEF\xBE\xAD\xDE",
};
const deadbeef = bytesToValue(u32, deadbeef_bytes);
testing.expect(deadbeef == u32(0xDEADBEEF));
}
fn SubArrayPtrReturnType(comptime T: type, comptime length: usize) type {
if (trait.isConstPtr(T))
return *const [length]meta.Child(meta.Child(T));
return *[length]meta.Child(meta.Child(T));
}
///Given a pointer to an array, returns a pointer to a portion of that array, preserving constness.
pub fn subArrayPtr(ptr: var, comptime start: usize, comptime length: usize) SubArrayPtrReturnType(@typeOf(ptr), length) {
assert(start + length <= ptr.*.len);
const ReturnType = SubArrayPtrReturnType(@typeOf(ptr), length);
const T = meta.Child(meta.Child(@typeOf(ptr)));
return @ptrCast(ReturnType, &ptr[start]);
}
test "subArrayPtr" {
const a1 = "abcdef";
const sub1 = subArrayPtr(&a1, 2, 3);
testing.expect(eql(u8, sub1.*, "cde"));
var a2 = "abcdef";
var sub2 = subArrayPtr(&a2, 2, 3);
testing.expect(eql(u8, sub2, "cde"));
sub2[1] = 'X';
testing.expect(eql(u8, a2, "abcXef"));
}
/// Round an address up to the nearest aligned address
/// The alignment must be a power of 2 and greater than 0.
pub fn alignForward(addr: usize, alignment: usize) usize {
return alignBackward(addr + (alignment - 1), alignment);
}
test "alignForward" {
testing.expect(alignForward(1, 1) == 1);
testing.expect(alignForward(2, 1) == 2);
testing.expect(alignForward(1, 2) == 2);
testing.expect(alignForward(2, 2) == 2);
testing.expect(alignForward(3, 2) == 4);
testing.expect(alignForward(4, 2) == 4);
testing.expect(alignForward(7, 8) == 8);
testing.expect(alignForward(8, 8) == 8);
testing.expect(alignForward(9, 8) == 16);
testing.expect(alignForward(15, 8) == 16);
testing.expect(alignForward(16, 8) == 16);
testing.expect(alignForward(17, 8) == 24);
}
/// Round an address up to the previous aligned address
/// The alignment must be a power of 2 and greater than 0.
pub fn alignBackward(addr: usize, alignment: usize) usize {
assert(@popCount(usize, alignment) == 1);
// 000010000 // example addr
// 000001111 // subtract 1
// 111110000 // binary not
return addr & ~(alignment - 1);
}
/// Given an address and an alignment, return true if the address is a multiple of the alignment
/// The alignment must be a power of 2 and greater than 0.
pub fn isAligned(addr: usize, alignment: usize) bool {
return alignBackward(addr, alignment) == addr;
}
test "isAligned" {
testing.expect(isAligned(0, 4));
testing.expect(isAligned(1, 1));
testing.expect(isAligned(2, 1));
testing.expect(isAligned(2, 2));
testing.expect(!isAligned(2, 4));
testing.expect(isAligned(3, 1));
testing.expect(!isAligned(3, 2));
testing.expect(!isAligned(3, 4));
testing.expect(isAligned(4, 4));
testing.expect(isAligned(4, 2));
testing.expect(isAligned(4, 1));
testing.expect(!isAligned(4, 8));
testing.expect(!isAligned(4, 16));
}