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const std = @import("std");
const testing = std.testing;
pub fn readULEB128(comptime T: type, in_stream: var) !T {
const ShiftT = @IntType(false, std.math.log2(T.bit_count));
var result: T = 0;
var shift: ShiftT = 0;
while (true) {
const byte = try in_stream.readByte();
var operand: T = undefined;
if (@shlWithOverflow(T, byte & 0x7f, shift, &operand))
return error.Overflow;
result |= operand;
if (@addWithOverflow(ShiftT, shift, 7, &shift))
return error.Overflow;
if ((byte & 0x80) == 0)
return result;
}
}
pub fn readULEB128Mem(comptime T: type, ptr: *[*]const u8) !T {
const ShiftT = @IntType(false, std.math.log2(T.bit_count));
var result: T = 0;
var shift: ShiftT = 0;
var i: usize = 0;
while (true) {
const byte = ptr.*[i];
i += 1;
var operand: T = undefined;
if (@shlWithOverflow(T, byte & 0x7f, shift, &operand))
return error.Overflow;
result |= operand;
if (@addWithOverflow(ShiftT, shift, 7, &shift))
return error.Overflow;
if ((byte & 0x80) == 0) {
ptr.* += i;
return result;
}
}
}
pub fn readILEB128(comptime T: type, in_stream: var) !T {
const ShiftT = @IntType(false, std.math.log2(T.bit_count));
var result: T = 0;
var shift: ShiftT = 0;
while (true) {
const byte = u8(try in_stream.readByte());
var operand: T = undefined;
if (@shlWithOverflow(T, @intCast(T, byte & 0x7f), shift, &operand))
return error.Overflow;
result |= operand;
if (@addWithOverflow(ShiftT, shift, 7, &shift))
return error.Overflow;
if ((byte & 0x80) == 0) {
if (shift <= ShiftT(T.bit_count - 1) and (byte & 0x40) != 0) {
result |= T(-1) << shift;
}
return result;
}
}
}
pub fn readILEB128Mem(comptime T: type, ptr: *[*]const u8) !T {
const ShiftT = @IntType(false, std.math.log2(T.bit_count));
var result: T = 0;
var shift: ShiftT = 0;
var i: usize = 0;
while (true) {
const byte = ptr.*[i];
i += 1;
var operand: T = undefined;
if (@shlWithOverflow(T, @intCast(T, byte & 0x7f), shift, &operand))
return error.Overflow;
result |= operand;
if (@addWithOverflow(ShiftT, shift, 7, &shift))
return error.Overflow;
if ((byte & 0x80) == 0) {
if (shift <= ShiftT(T.bit_count - 1) and (byte & 0x40) != 0) {
result |= T(-1) << shift;
}
ptr.* += i;
return result;
}
}
}
const OneByteReadInStream = struct {
const Error = error{NoError};
const Stream = std.io.InStream(Error);
stream: Stream,
str: []const u8,
curr: usize,
fn init(str: []const u8) @This() {
return @This(){
.stream = Stream{ .readFn = readFn },
.str = str,
.curr = 0,
};
}
fn readFn(in_stream: *Stream, dest: []u8) Error!usize {
const self = @fieldParentPtr(@This(), "stream", in_stream);
if (self.str.len <= self.curr or dest.len == 0)
return 0;
dest[0] = self.str[self.curr];
self.curr += 1;
return 1;
}
};
fn test_read_ileb128(comptime T: type, encoded: []const u8) !T {
var in_stream = OneByteReadInStream.init(encoded);
const v1 = try readILEB128(T, &in_stream.stream);
var in_ptr = encoded.ptr;
const v2 = try readILEB128Mem(T, &in_ptr);
testing.expectEqual(v1, v2);
return v2;
}
fn test_read_uleb128(comptime T: type, encoded: []const u8) !T {
var in_stream = OneByteReadInStream.init(encoded);
const v1 = try readULEB128(T, &in_stream.stream);
var in_ptr = encoded.ptr;
const v2 = try readULEB128Mem(T, &in_ptr);
return v2;
}
test "deserialize signed LEB128" {
// Truncated
testing.expectError(error.EndOfStream, test_read_ileb128(i64, "\x80"));
// Overflow
testing.expectError(error.Overflow, test_read_ileb128(i8, "\x80\x80\x40"));
testing.expectError(error.Overflow, test_read_ileb128(i16, "\x80\x80\x80\x40"));
testing.expectError(error.Overflow, test_read_ileb128(i32, "\x80\x80\x80\x80\x40"));
testing.expectError(error.Overflow, test_read_ileb128(i64, "\x80\x80\x80\x80\x80\x80\x80\x80\x80\x40"));
// Decode SLEB128
testing.expect((try test_read_ileb128(i64, "\x00")) == 0);
testing.expect((try test_read_ileb128(i64, "\x01")) == 1);
testing.expect((try test_read_ileb128(i64, "\x3f")) == 63);
testing.expect((try test_read_ileb128(i64, "\x40")) == -64);
testing.expect((try test_read_ileb128(i64, "\x41")) == -63);
testing.expect((try test_read_ileb128(i64, "\x7f")) == -1);
testing.expect((try test_read_ileb128(i64, "\x80\x01")) == 128);
testing.expect((try test_read_ileb128(i64, "\x81\x01")) == 129);
testing.expect((try test_read_ileb128(i64, "\xff\x7e")) == -129);
testing.expect((try test_read_ileb128(i64, "\x80\x7f")) == -128);
testing.expect((try test_read_ileb128(i64, "\x81\x7f")) == -127);
testing.expect((try test_read_ileb128(i64, "\xc0\x00")) == 64);
testing.expect((try test_read_ileb128(i64, "\xc7\x9f\x7f")) == -12345);
// Decode unnormalized SLEB128 with extra padding bytes.
testing.expect((try test_read_ileb128(i64, "\x80\x00")) == 0);
testing.expect((try test_read_ileb128(i64, "\x80\x80\x00")) == 0);
testing.expect((try test_read_ileb128(i64, "\xff\x00")) == 0x7f);
testing.expect((try test_read_ileb128(i64, "\xff\x80\x00")) == 0x7f);
testing.expect((try test_read_ileb128(i64, "\x80\x81\x00")) == 0x80);
testing.expect((try test_read_ileb128(i64, "\x80\x81\x80\x00")) == 0x80);
}
test "deserialize unsigned LEB128" {
// Truncated
testing.expectError(error.EndOfStream, test_read_uleb128(u64, "\x80"));
// Overflow
testing.expectError(error.Overflow, test_read_uleb128(u8, "\x80\x80\x40"));
testing.expectError(error.Overflow, test_read_uleb128(u16, "\x80\x80\x80\x40"));
testing.expectError(error.Overflow, test_read_uleb128(u32, "\x80\x80\x80\x80\x40"));
testing.expectError(error.Overflow, test_read_uleb128(u64, "\x80\x80\x80\x80\x80\x80\x80\x80\x80\x40"));
// Decode ULEB128
testing.expect((try test_read_uleb128(u64, "\x00")) == 0);
testing.expect((try test_read_uleb128(u64, "\x01")) == 1);
testing.expect((try test_read_uleb128(u64, "\x3f")) == 63);
testing.expect((try test_read_uleb128(u64, "\x40")) == 64);
testing.expect((try test_read_uleb128(u64, "\x7f")) == 0x7f);
testing.expect((try test_read_uleb128(u64, "\x80\x01")) == 0x80);
testing.expect((try test_read_uleb128(u64, "\x81\x01")) == 0x81);
testing.expect((try test_read_uleb128(u64, "\x90\x01")) == 0x90);
testing.expect((try test_read_uleb128(u64, "\xff\x01")) == 0xff);
testing.expect((try test_read_uleb128(u64, "\x80\x02")) == 0x100);
testing.expect((try test_read_uleb128(u64, "\x81\x02")) == 0x101);
testing.expect((try test_read_uleb128(u64, "\x80\xc1\x80\x80\x10")) == 4294975616);
// Decode ULEB128 with extra padding bytes
testing.expect((try test_read_uleb128(u64, "\x80\x00")) == 0);
testing.expect((try test_read_uleb128(u64, "\x80\x80\x00")) == 0);
testing.expect((try test_read_uleb128(u64, "\xff\x00")) == 0x7f);
testing.expect((try test_read_uleb128(u64, "\xff\x80\x00")) == 0x7f);
testing.expect((try test_read_uleb128(u64, "\x80\x81\x00")) == 0x80);
testing.expect((try test_read_uleb128(u64, "\x80\x81\x80\x00")) == 0x80);
}
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