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// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "gpu/command_buffer/common/mailbox.h"
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include "base/check.h"
#include "base/numerics/byte_conversions.h"
#include "base/rand_util.h"
#include "base/strings/stringprintf.h"
namespace gpu {
namespace {
// The last byte of the mailbox's name stores a bit that ensures that the
// mailbox doesn't end up being generated as zero. This avoids conflicts with
// Verify logic, which uses the first byte.
constexpr size_t kLiveMailboxIndex = GL_MAILBOX_SIZE_CHROMIUM - 1;
// Use the lowest bit for the flag marking the mailbox as live (any bit would
// work).
constexpr int8_t kLiveMailboxFlag = 0x1;
} // namespace
Mailbox::Mailbox() {
memset(name, 0, sizeof(name));
}
bool Mailbox::IsZero() const {
for (size_t i = 0; i < std::size(name); ++i) {
if (name[i])
return false;
}
return true;
}
void Mailbox::SetZero() {
memset(name, 0, sizeof(name));
}
void Mailbox::SetName(const int8_t* n) {
DCHECK(IsZero() || !memcmp(name, n, sizeof(name)));
memcpy(name, n, sizeof(name));
}
Mailbox Mailbox::Generate() {
Mailbox result;
// Generates cryptographically-secure bytes.
base::RandBytes(base::as_writable_byte_span(result.name));
// Ensure that the mailbox is non-zero.
result.name[kLiveMailboxIndex] |= kLiveMailboxFlag;
#if !defined(NDEBUG)
int8_t value = 1;
for (size_t i = 1; i < sizeof(result.name); ++i) {
value ^= result.name[i];
}
result.name[0] = value;
#endif
return result;
}
bool Mailbox::Verify() const {
#if !defined(NDEBUG)
int8_t value = 1;
for (size_t i = 0; i < sizeof(name); ++i)
value ^= name[i];
return value == 0;
#else
return true;
#endif
}
uint32_t Mailbox::ToU32() const {
return base::U32FromBigEndian(base::as_byte_span(name).first<4>());
}
std::string Mailbox::ToDebugString() const {
std::string s;
for (int i = 0; i < GL_MAILBOX_SIZE_CHROMIUM; ++i) {
if (i > 0)
s += ':';
s += base::StringPrintf("%02X", static_cast<uint8_t>(name[i]));
}
return s;
}
bool Mailbox::operator==(const Mailbox& other) const {
return memcmp(&name, &other.name, sizeof(name)) == 0;
}
std::strong_ordering Mailbox::operator<=>(const Mailbox& other) const {
int result = memcmp(&name, &other.name, sizeof(name));
if (result < 0) {
return std::strong_ordering::less;
} else if (result > 0) {
return std::strong_ordering::greater;
}
return std::strong_ordering::equal;
}
} // namespace gpu
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