From 772876b2f0104953af56eccbd85b2b21c6e908ef Mon Sep 17 00:00:00 2001 From: Josh Wolfe Date: Wed, 7 Nov 2018 20:50:10 -0500 Subject: [PATCH] implement mem.writeIntLE, mem.writeIntBE --- std/mem.zig | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) diff --git a/std/mem.zig b/std/mem.zig index 26fa8915b..24c1abac1 100644 --- a/std/mem.zig +++ b/std/mem.zig @@ -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;