RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-26 21:47:46 +00:00
Code Issues Activity Actions

AK: Port LEB128 to the new AK::Stream

Browse source
This commit is contained in:
Tim Schumacher 2023-01-29 13:09:25 +01:00 • committed by Andrew Kaster
parent 31f59855b4
commit 787f4d639a
10 changed files with 120 additions and 209 deletions
Download patch file Download diff file Expand all files Collapse all files

42
AK/LEB128.h
View file

@ -6,36 +6,32 @@
#pragma once
#include <AK/DeprecatedStream.h>
#include <AK/NumericLimits.h>
#include <AK/Stream.h>
#include <AK/Types.h>
namespace AK {
struct LEB128 {
template<typename ValueType = size_t>
static bool read_unsigned(DeprecatedInputStream& stream, ValueType& result)
static ErrorOr<void> read_unsigned(AK::Stream& stream, ValueType& result)
{
result = 0;
size_t num_bytes = 0;
while (true) {
if (stream.unreliable_eof()) {
stream.set_fatal_error();
return false;
}
u8 byte = 0;
stream >> byte;
if (stream.has_any_error())
return false;
if (stream.is_eof())
return Error::from_string_literal("Stream reached end-of-file while reading LEB128 value");
auto byte = TRY(stream.read_value<u8>());
ValueType masked_byte = byte & ~(1 << 7);
bool const shift_too_large_for_result = num_bytes * 7 > sizeof(ValueType) * 8;
if (shift_too_large_for_result)
return false;
return Error::from_string_literal("Read value contains more bits than fit the chosen ValueType");
bool const shift_too_large_for_byte = ((masked_byte << (num_bytes * 7)) >> (num_bytes * 7)) != masked_byte;
if (shift_too_large_for_byte)
return false;
return Error::from_string_literal("Read byte is too large to fit the chosen ValueType");
result = (result) | (masked_byte << (num_bytes * 7));
if (!(byte & (1 << 7)))
@ -43,11 +39,11 @@ struct LEB128 {
++num_bytes;
}
return true;
return {};
}
template<typename ValueType = ssize_t>
static bool read_signed(DeprecatedInputStream& stream, ValueType& result)
static ErrorOr<void> read_signed(AK::Stream& stream, ValueType& result)
{
// Note: We read into a u64 to simplify the parsing logic;
// result is range checked into ValueType after parsing.
@ -59,24 +55,20 @@ struct LEB128 {
result = 0;
do {
if (stream.unreliable_eof()) {
stream.set_fatal_error();
return false;
}
if (stream.is_eof())
return Error::from_string_literal("Stream reached end-of-file while reading LEB128 value");
stream >> byte;
if (stream.has_any_error())
return false;
byte = TRY(stream.read_value<u8>());
// note: 64 bit assumptions!
u64 masked_byte = byte & ~(1 << 7);
bool const shift_too_large_for_result = num_bytes * 7 >= 64;
if (shift_too_large_for_result)
return false;
return Error::from_string_literal("Read value contains more bits than fit the chosen ValueType");
bool const shift_too_large_for_byte = (num_bytes * 7) == 63 && masked_byte != 0x00 && masked_byte != 0x7Fu;
if (shift_too_large_for_byte)
return false;
return Error::from_string_literal("Read byte is too large to fit the chosen ValueType");
temp = (temp) | (masked_byte << (num_bytes * 7));
++num_bytes;
@ -90,12 +82,12 @@ struct LEB128 {
// Now that we've accumulated into an i64, make sure it fits into result
if constexpr (sizeof(ValueType) < sizeof(u64)) {
if (temp > NumericLimits<ValueType>::max() || temp < NumericLimits<ValueType>::min())
return false;
return Error::from_string_literal("Temporary value does not fit the result type");
}
result = static_cast<ValueType>(temp);
return true;
return {};
}
};