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implement mem.writeIntLE, mem.writeIntBE

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This commit is contained in:
Josh Wolfe 2018-11-07 20:50:10 -05:00
parent 8d8836c2d1
commit 772876b2f0
1 changed files with 80 additions and 0 deletions
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80
std/mem.zig
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@ -439,6 +439,7 @@ pub fn readIntBE(comptime T: type, bytes: []const u8) T {
return @bitCast(T, readIntBE(@IntType(false, T.bit_count), bytes));
}
assert(bytes.len == @sizeOf(T));
if (T == u8) return bytes[0];
var result: T = 0;
{
comptime var i = 0;
@ -456,6 +457,7 @@ pub fn readIntLE(comptime T: type, bytes: []const u8) T {
return @bitCast(T, readIntLE(@IntType(false, T.bit_count), bytes));
}
assert(bytes.len == @sizeOf(T));
if (T == u8) return bytes[0];
var result: T = 0;
{
comptime var i = 0;
@ -492,6 +494,84 @@ pub fn writeInt(buf: []u8, value: var, endian: builtin.Endian) void {
assert(bits == 0);
}
pub fn writeIntBE(comptime T: type, buf: *[@sizeOf(T)]u8, value: T) void {
assert(T.bit_count % 8 == 0);
const uint = @IntType(false, T.bit_count);
if (uint == u0) {
return;
}
var bits = @bitCast(uint, value);
if (uint == u8) {
buf[0] = bits;
return;
}
var index: usize = buf.len;
while (index != 0) {
index -= 1;
buf[index] = @truncate(u8, bits);
bits >>= 8;
}
assert(bits == 0);
}
pub fn writeIntLE(comptime T: type, buf: *[@sizeOf(T)]u8, value: T) void {
assert(T.bit_count % 8 == 0);
const uint = @IntType(false, T.bit_count);
if (uint == u0) {
return;
}
var bits = @bitCast(uint, value);
if (uint == u8) {
buf[0] = bits;
return;
}
// FIXME: this should just be for (buf).
// See https://github.com/ziglang/zig/issues/1663
for (buf.*) |*b| {
b.* = @truncate(u8, bits);
bits >>= 8;
}
assert(bits == 0);
}
test "writeIntBE/LE" {
var buf0: [0]u8 = undefined;
var buf1: [1]u8 = undefined;
var buf2: [2]u8 = undefined;
var buf9: [9]u8 = undefined;
writeIntBE(u0, &buf0, 0x0);
assert(eql_slice_u8(buf0[0..], []u8{}));
writeIntLE(u0, &buf0, 0x0);
assert(eql_slice_u8(buf0[0..], []u8{}));
writeIntBE(u8, &buf1, 0x12);
assert(eql_slice_u8(buf1[0..], []u8{0x12}));
writeIntLE(u8, &buf1, 0x34);
assert(eql_slice_u8(buf1[0..], []u8{0x34}));
writeIntBE(u16, &buf2, 0x1234);
assert(eql_slice_u8(buf2[0..], []u8{ 0x12, 0x34 }));
writeIntLE(u16, &buf2, 0x5678);
assert(eql_slice_u8(buf2[0..], []u8{ 0x78, 0x56 }));
writeIntBE(u72, &buf9, 0x123456789abcdef024);
assert(eql_slice_u8(buf9[0..], []u8{ 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0, 0x24 }));
writeIntLE(u72, &buf9, 0xfedcba9876543210ec);
assert(eql_slice_u8(buf9[0..], []u8{ 0xec, 0x10, 0x32, 0x54, 0x76, 0x98, 0xba, 0xdc, 0xfe }));
writeIntBE(i8, &buf1, -1);
assert(eql_slice_u8(buf1[0..], []u8{0xff}));
writeIntLE(i8, &buf1, -2);
assert(eql_slice_u8(buf1[0..], []u8{0xfe}));
writeIntBE(i16, &buf2, -3);
assert(eql_slice_u8(buf2[0..], []u8{ 0xff, 0xfd }));
writeIntLE(i16, &buf2, -4);
assert(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;