mirror of
https://github.com/ziglang/zig.git
synced 2026-02-13 04:48:20 +00:00
Fix up sign handling and add arbitrary-length integer support to @bitCast()
This commit is contained in:
Cody Tapscott
parent
e1a535360f
commit
70d7f87be0
@ -1,4 +1,5 @@
|
||||
const std = @import("../../std.zig");
|
||||
const builtin = @import("builtin");
|
||||
const math = std.math;
|
||||
const Limb = std.math.big.Limb;
|
||||
const limb_bits = @typeInfo(Limb).Int.bits;
|
||||
@ -14,6 +15,7 @@ const minInt = std.math.minInt;
|
||||
const assert = std.debug.assert;
|
||||
const Endian = std.builtin.Endian;
|
||||
const Signedness = std.builtin.Signedness;
|
||||
const native_endian = builtin.cpu.arch.endian();
|
||||
|
||||
const debug_safety = false;
|
||||
|
||||
@ -1621,6 +1623,15 @@ pub const Mutable = struct {
|
||||
}
|
||||
}
|
||||
|
||||
/// Read the value of `x` from `buffer`
|
||||
/// Asserts that `buffer` and `bit_count` are large enough to store the value.
|
||||
///
|
||||
/// For integers with a well-defined layout (e.g. all power-of-two integers), this function
|
||||
/// reads from `buffer` as if it were the contents of @ptrCast([]const u8, &x), where the
|
||||
/// slice length is taken to be @sizeOf(std.meta.Int(signedness, <bit_count>))
|
||||
///
|
||||
/// For integers with a non-well-defined layout, `buffer` must have been created by
|
||||
/// writeTwosComplement.
|
||||
pub fn readTwosComplement(
|
||||
x: *Mutable,
|
||||
buffer: []const u8,
|
||||
@ -1634,26 +1645,77 @@ pub const Mutable = struct {
|
||||
x.positive = true;
|
||||
return;
|
||||
}
|
||||
// zig fmt: off
|
||||
switch (signedness) {
|
||||
.signed => {
|
||||
if (bit_count <= 8) return x.set(mem.readInt( i8, buffer[0.. 1], endian));
|
||||
if (bit_count <= 16) return x.set(mem.readInt( i16, buffer[0.. 2], endian));
|
||||
if (bit_count <= 32) return x.set(mem.readInt( i32, buffer[0.. 4], endian));
|
||||
if (bit_count <= 64) return x.set(mem.readInt( i64, buffer[0.. 8], endian));
|
||||
if (bit_count <= 128) return x.set(mem.readInt(i128, buffer[0..16], endian));
|
||||
},
|
||||
.unsigned => {
|
||||
if (bit_count <= 8) return x.set(mem.readInt( u8, buffer[0.. 1], endian));
|
||||
if (bit_count <= 16) return x.set(mem.readInt( u16, buffer[0.. 2], endian));
|
||||
if (bit_count <= 32) return x.set(mem.readInt( u32, buffer[0.. 4], endian));
|
||||
if (bit_count <= 64) return x.set(mem.readInt( u64, buffer[0.. 8], endian));
|
||||
if (bit_count <= 128) return x.set(mem.readInt(u128, buffer[0..16], endian));
|
||||
},
|
||||
}
|
||||
// zig fmt: on
|
||||
|
||||
@panic("TODO implement std lib big int readTwosComplement");
|
||||
// byte_count is the total amount of bytes to read from buffer
|
||||
var byte_count = @sizeOf(Limb) * (bit_count / @bitSizeOf(Limb));
|
||||
if (bit_count % @bitSizeOf(Limb) != 0) { // Round up to a power-of-two integer <= Limb
|
||||
byte_count += (std.math.ceilPowerOfTwoAssert(usize, bit_count % @bitSizeOf(Limb)) + 7) / 8;
|
||||
}
|
||||
|
||||
const limb_count = calcTwosCompLimbCount(8 * byte_count);
|
||||
|
||||
// Check whether the input is negative
|
||||
var positive = true;
|
||||
if (signedness == .signed) {
|
||||
var last_byte = switch (endian) {
|
||||
.Little => ((bit_count + 7) / 8) - 1,
|
||||
.Big => byte_count - ((bit_count + 7) / 8),
|
||||
};
|
||||
|
||||
const sign_bit = @as(u8, 1) << @intCast(u3, (bit_count - 1) % 8);
|
||||
positive = ((buffer[last_byte] & sign_bit) == 0);
|
||||
}
|
||||
|
||||
// Copy all complete limbs
|
||||
var carry: u1 = if (positive) 0 else 1;
|
||||
var limb_index: usize = 0;
|
||||
while (limb_index < bit_count / @bitSizeOf(Limb)) : (limb_index += 1) {
|
||||
var buf_index = switch (endian) {
|
||||
.Little => @sizeOf(Limb) * limb_index,
|
||||
.Big => byte_count - (limb_index + 1) * @sizeOf(Limb),
|
||||
};
|
||||
|
||||
const limb_buf = @ptrCast(*const [@sizeOf(Limb)]u8, buffer[buf_index..]);
|
||||
var limb = mem.readInt(Limb, limb_buf, endian);
|
||||
|
||||
// 2's complement (bitwise not, then add carry bit)
|
||||
if (!positive) carry = @boolToInt(@addWithOverflow(Limb, ~limb, carry, &limb));
|
||||
x.limbs[limb_index] = limb;
|
||||
}
|
||||
|
||||
// Copy any remaining bytes, using the nearest power-of-two integer that is large enough
|
||||
const bits_left = @intCast(Log2Limb, bit_count % @bitSizeOf(Limb));
|
||||
if (bits_left != 0) {
|
||||
const bytes_read = limb_index * @sizeOf(Limb);
|
||||
const bytes_left = byte_count - bytes_read;
|
||||
var buffer_left = switch (endian) {
|
||||
.Little => buffer[bytes_read..],
|
||||
.Big => buffer[0..],
|
||||
};
|
||||
|
||||
var limb = @intCast(Limb, blk: {
|
||||
// zig fmt: off
|
||||
if (bytes_left == 1) break :blk mem.readInt( u8, buffer_left[0.. 1], endian);
|
||||
if (bytes_left == 2) break :blk mem.readInt( u16, buffer_left[0.. 2], endian);
|
||||
if (bytes_left == 4) break :blk mem.readInt( u32, buffer_left[0.. 4], endian);
|
||||
if (bytes_left == 8) break :blk mem.readInt( u64, buffer_left[0.. 8], endian);
|
||||
if (bytes_left == 16) break :blk mem.readInt(u128, buffer_left[0..16], endian);
|
||||
// zig fmt: on
|
||||
unreachable;
|
||||
});
|
||||
|
||||
// 2's complement (bitwise not, then add carry bit)
|
||||
if (!positive) _ = @addWithOverflow(Limb, ~limb, carry, &limb);
|
||||
|
||||
// Mask off any unused bits
|
||||
const mask = (@as(Limb, 1) << bits_left) -% 1; // 0b0..01..1 with (bits_left) trailing ones
|
||||
limb &= mask;
|
||||
|
||||
x.limbs[limb_count - 1] = limb;
|
||||
}
|
||||
x.positive = positive;
|
||||
x.len = limb_count;
|
||||
x.normalize(x.len);
|
||||
}
|
||||
|
||||
/// Normalize a possible sequence of leading zeros.
|
||||
@ -1806,7 +1868,7 @@ pub const Const = struct {
|
||||
.Int => |info| {
|
||||
const UT = std.meta.Int(.unsigned, info.bits);
|
||||
|
||||
if (self.bitCountTwosComp() > info.bits) {
|
||||
if (!self.fitsInTwosComp(info.signedness, info.bits)) {
|
||||
return error.TargetTooSmall;
|
||||
}
|
||||
|
||||
@ -2013,27 +2075,69 @@ pub const Const = struct {
|
||||
return s.len;
|
||||
}
|
||||
|
||||
/// Write the value of `x` into `buffer`
|
||||
/// Asserts that `buffer` and `bit_count` are large enough to store the value.
|
||||
///
|
||||
/// For integers with a well-defined layout (e.g. all power-of-two integers), this function
|
||||
/// can be thought of as writing to `buffer` the contents of @ptrCast([]const u8, &x),
|
||||
/// where the slice length is taken to be @sizeOf(std.meta.Int(_,<bit_count>))
|
||||
///
|
||||
/// For integers with a non-well-defined layout, the only requirement is that readTwosComplement
|
||||
/// on the same buffer creates an equivalent big integer.
|
||||
pub fn writeTwosComplement(x: Const, buffer: []u8, bit_count: usize, endian: Endian) void {
|
||||
if (bit_count == 0) return;
|
||||
|
||||
// zig fmt: off
|
||||
if (x.positive) {
|
||||
if (bit_count <= 8) return mem.writeInt( u8, buffer[0.. 1], x.to( u8) catch unreachable, endian);
|
||||
if (bit_count <= 16) return mem.writeInt( u16, buffer[0.. 2], x.to( u16) catch unreachable, endian);
|
||||
if (bit_count <= 32) return mem.writeInt( u32, buffer[0.. 4], x.to( u32) catch unreachable, endian);
|
||||
if (bit_count <= 64) return mem.writeInt( u64, buffer[0.. 8], x.to( u64) catch unreachable, endian);
|
||||
if (bit_count <= 128) return mem.writeInt(u128, buffer[0..16], x.to(u128) catch unreachable, endian);
|
||||
} else {
|
||||
if (bit_count <= 8) return mem.writeInt( i8, buffer[0.. 1], x.to( i8) catch unreachable, endian);
|
||||
if (bit_count <= 16) return mem.writeInt( i16, buffer[0.. 2], x.to( i16) catch unreachable, endian);
|
||||
if (bit_count <= 32) return mem.writeInt( i32, buffer[0.. 4], x.to( i32) catch unreachable, endian);
|
||||
if (bit_count <= 64) return mem.writeInt( i64, buffer[0.. 8], x.to( i64) catch unreachable, endian);
|
||||
if (bit_count <= 128) return mem.writeInt(i128, buffer[0..16], x.to(i128) catch unreachable, endian);
|
||||
var byte_count = @sizeOf(Limb) * (bit_count / @bitSizeOf(Limb));
|
||||
if (bit_count % @bitSizeOf(Limb) != 0) {
|
||||
byte_count += (std.math.ceilPowerOfTwoAssert(usize, bit_count % @bitSizeOf(Limb)) + 7) / 8;
|
||||
}
|
||||
// zig fmt: on
|
||||
assert(buffer.len >= byte_count);
|
||||
assert(x.fitsInTwosComp(if (x.positive) .unsigned else .signed, bit_count));
|
||||
|
||||
@panic("TODO implement std lib big int writeTwosComplement for larger than 128 bits");
|
||||
// Copy all complete limbs
|
||||
var carry: u1 = if (x.positive) 0 else 1;
|
||||
var limb_index: usize = 0;
|
||||
while (limb_index < byte_count / @sizeOf(Limb)) : (limb_index += 1) {
|
||||
var buf_index = switch (endian) {
|
||||
.Little => @sizeOf(Limb) * limb_index,
|
||||
.Big => byte_count - (limb_index + 1) * @sizeOf(Limb),
|
||||
};
|
||||
|
||||
var limb: Limb = if (limb_index < x.limbs.len) x.limbs[limb_index] else 0;
|
||||
// 2's complement (bitwise not, then add carry bit)
|
||||
if (!x.positive) carry = @boolToInt(@addWithOverflow(Limb, ~limb, carry, &limb));
|
||||
|
||||
var limb_buf = @ptrCast(*[@sizeOf(Limb)]u8, buffer[buf_index..]);
|
||||
mem.writeInt(Limb, limb_buf, limb, endian);
|
||||
}
|
||||
|
||||
// Copy any remaining bytes
|
||||
if (byte_count % @sizeOf(Limb) != 0) {
|
||||
const bytes_read = limb_index * @sizeOf(Limb);
|
||||
const bytes_left = byte_count - bytes_read;
|
||||
var buffer_left = switch (endian) {
|
||||
.Little => buffer[bytes_read..],
|
||||
.Big => buffer[0..],
|
||||
};
|
||||
|
||||
var limb: Limb = if (limb_index < x.limbs.len) x.limbs[limb_index] else 0;
|
||||
// 2's complement (bitwise not, then add carry bit)
|
||||
if (!x.positive) _ = @addWithOverflow(Limb, ~limb, carry, &limb);
|
||||
|
||||
if (bytes_left == 1) {
|
||||
mem.writeInt(u8, buffer_left[0..1], @truncate(u8, limb), endian);
|
||||
} else if (@sizeOf(Limb) > 1 and bytes_left == 2) {
|
||||
mem.writeInt(u16, buffer_left[0..2], @truncate(u16, limb), endian);
|
||||
} else if (@sizeOf(Limb) > 2 and bytes_left == 4) {
|
||||
mem.writeInt(u32, buffer_left[0..4], @truncate(u32, limb), endian);
|
||||
} else if (@sizeOf(Limb) > 4 and bytes_left == 8) {
|
||||
mem.writeInt(u64, buffer_left[0..8], @truncate(u64, limb), endian);
|
||||
} else if (@sizeOf(Limb) > 8 and bytes_left == 16) {
|
||||
mem.writeInt(u128, buffer_left[0..16], @truncate(u128, limb), endian);
|
||||
} else if (@sizeOf(Limb) > 16) {
|
||||
@compileError("@sizeOf(Limb) exceeded supported range");
|
||||
} else unreachable;
|
||||
}
|
||||
}
|
||||
|
||||
/// Returns `math.Order.lt`, `math.Order.eq`, `math.Order.gt` if
|
||||
|
||||
@ -2486,3 +2486,28 @@ test "big int popcount" {
|
||||
|
||||
try testing.expect(a.toConst().orderAgainstScalar(16) == .eq);
|
||||
}
|
||||
|
||||
test "big int conversion read/write twos complement" {
|
||||
var a = try Managed.initSet(testing.allocator, (1 << 493) - 1);
|
||||
defer a.deinit();
|
||||
var b = try Managed.initSet(testing.allocator, (1 << 493) - 1);
|
||||
defer b.deinit();
|
||||
var m = b.toMutable();
|
||||
|
||||
var buffer1 = try testing.allocator.alloc(u8, 64);
|
||||
defer testing.allocator.free(buffer1);
|
||||
|
||||
const endians = [_]std.builtin.Endian{ .Little, .Big };
|
||||
|
||||
for (endians) |endian| {
|
||||
// Writing to buffer and back should not change anything
|
||||
a.toConst().writeTwosComplement(buffer1, 493, endian);
|
||||
m.readTwosComplement(buffer1, 493, endian, .unsigned);
|
||||
try testing.expect(m.toConst().order(a.toConst()) == .eq);
|
||||
|
||||
// Equivalent to @bitCast(i493, @as(u493, intMax(u493))
|
||||
a.toConst().writeTwosComplement(buffer1, 493, endian);
|
||||
m.readTwosComplement(buffer1, 493, endian, .signed);
|
||||
try testing.expect(m.toConst().orderAgainstScalar(-1) == .eq);
|
||||
}
|
||||
}
|
||||
|
||||
@ -1093,8 +1093,9 @@ pub const Value = extern union {
|
||||
.Int => {
|
||||
const int_info = ty.intInfo(target);
|
||||
const endian = target.cpu.arch.endian();
|
||||
// TODO use a correct amount of limbs
|
||||
const limbs_buffer = try arena.alloc(std.math.big.Limb, 2);
|
||||
const Limb = std.math.big.Limb;
|
||||
const limb_count = (buffer.len + @sizeOf(Limb) - 1) / @sizeOf(Limb);
|
||||
const limbs_buffer = try arena.alloc(Limb, limb_count);
|
||||
var bigint = BigIntMutable.init(limbs_buffer, 0);
|
||||
bigint.readTwosComplement(buffer, int_info.bits, endian, int_info.signedness);
|
||||
return fromBigInt(arena, bigint.toConst());
|
||||
|
||||
@ -3,6 +3,7 @@ const builtin = @import("builtin");
|
||||
const expect = std.testing.expect;
|
||||
const expectEqual = std.testing.expectEqual;
|
||||
const maxInt = std.math.maxInt;
|
||||
const minInt = std.math.minInt;
|
||||
const native_endian = builtin.target.cpu.arch.endian();
|
||||
|
||||
test "@bitCast i32 -> u32" {
|
||||
@ -11,21 +12,119 @@ test "@bitCast i32 -> u32" {
|
||||
}
|
||||
|
||||
fn testBitCast_i32_u32() !void {
|
||||
try expect(conv(-1) == maxInt(u32));
|
||||
try expect(conv2(maxInt(u32)) == -1);
|
||||
try expect(conv_i32(-1) == maxInt(u32));
|
||||
try expect(conv_u32(maxInt(u32)) == -1);
|
||||
try expect(conv_u32(0x8000_0000) == minInt(i32));
|
||||
try expect(conv_i32(minInt(i32)) == 0x8000_0000);
|
||||
}
|
||||
|
||||
fn conv(x: i32) u32 {
|
||||
fn conv_i32(x: i32) u32 {
|
||||
return @bitCast(u32, x);
|
||||
}
|
||||
fn conv2(x: u32) i32 {
|
||||
fn conv_u32(x: u32) i32 {
|
||||
return @bitCast(i32, x);
|
||||
}
|
||||
|
||||
test "@bitCast i48 -> u48" {
|
||||
try testBitCast_i48_u48();
|
||||
comptime try testBitCast_i48_u48();
|
||||
}
|
||||
|
||||
fn testBitCast_i48_u48() !void {
|
||||
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
|
||||
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
|
||||
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
|
||||
|
||||
try expect(conv_i48(-1) == maxInt(u48));
|
||||
try expect(conv_u48(maxInt(u48)) == -1);
|
||||
try expect(conv_u48(0x8000_0000_0000) == minInt(i48));
|
||||
try expect(conv_i48(minInt(i48)) == 0x8000_0000_0000);
|
||||
}
|
||||
|
||||
fn conv_i48(x: i48) u48 {
|
||||
return @bitCast(u48, x);
|
||||
}
|
||||
|
||||
fn conv_u48(x: u48) i48 {
|
||||
return @bitCast(i48, x);
|
||||
}
|
||||
|
||||
test "@bitCast i27 -> u27" {
|
||||
try testBitCast_i27_u27();
|
||||
comptime try testBitCast_i27_u27();
|
||||
}
|
||||
|
||||
fn testBitCast_i27_u27() !void {
|
||||
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
|
||||
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
|
||||
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
|
||||
|
||||
try expect(conv_i27(-1) == maxInt(u27));
|
||||
try expect(conv_u27(maxInt(u27)) == -1);
|
||||
try expect(conv_u27(0x400_0000) == minInt(i27));
|
||||
try expect(conv_i27(minInt(i27)) == 0x400_0000);
|
||||
}
|
||||
|
||||
fn conv_i27(x: i27) u27 {
|
||||
return @bitCast(u27, x);
|
||||
}
|
||||
|
||||
fn conv_u27(x: u27) i27 {
|
||||
return @bitCast(i27, x);
|
||||
}
|
||||
|
||||
test "@bitCast i512 -> u512" {
|
||||
try testBitCast_i512_u512();
|
||||
comptime try testBitCast_i512_u512();
|
||||
}
|
||||
|
||||
fn testBitCast_i512_u512() !void {
|
||||
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
|
||||
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
|
||||
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
|
||||
|
||||
try expect(conv_i512(-1) == maxInt(u512));
|
||||
try expect(conv_u512(maxInt(u512)) == -1);
|
||||
try expect(conv_u512(@as(u512, 1) << 511) == minInt(i512));
|
||||
try expect(conv_i512(minInt(i512)) == (@as(u512, 1) << 511));
|
||||
}
|
||||
|
||||
fn conv_i512(x: i512) u512 {
|
||||
return @bitCast(u512, x);
|
||||
}
|
||||
|
||||
fn conv_u512(x: u512) i512 {
|
||||
return @bitCast(i512, x);
|
||||
}
|
||||
|
||||
test "bitcast result to _" {
|
||||
_ = @bitCast(u8, @as(i8, 1));
|
||||
}
|
||||
|
||||
test "@bitCast i493 -> u493" {
|
||||
try testBitCast_i493_u493();
|
||||
comptime try testBitCast_i493_u493();
|
||||
}
|
||||
|
||||
fn testBitCast_i493_u493() !void {
|
||||
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
|
||||
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
|
||||
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
|
||||
|
||||
try expect(conv_i493(-1) == maxInt(u493));
|
||||
try expect(conv_u493(maxInt(u493)) == -1);
|
||||
try expect(conv_u493(@as(u493, 1) << 492) == minInt(i493));
|
||||
try expect(conv_i493(minInt(i493)) == (@as(u493, 1) << 492));
|
||||
}
|
||||
|
||||
fn conv_i493(x: i493) u493 {
|
||||
return @bitCast(u493, x);
|
||||
}
|
||||
|
||||
fn conv_u493(x: u493) i493 {
|
||||
return @bitCast(i493, x);
|
||||
}
|
||||
|
||||
test "nested bitcast" {
|
||||
const S = struct {
|
||||
fn moo(x: isize) !void {
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user