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// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_WASM_LEB_HELPER_H_
#define V8_WASM_LEB_HELPER_H_
#include <cstddef>
#include <cstdint>
namespace v8 {
namespace internal {
namespace wasm {
constexpr size_t kPaddedVarInt32Size = 5;
constexpr size_t kMaxVarInt32Size = 5;
constexpr size_t kMaxVarInt64Size = 10;
class LEBHelper {
public:
// Write a 32-bit unsigned LEB to {dest}, updating {dest} to point after
// the last uint8_t written. No safety checks.
static void write_u32v(uint8_t** dest, uint32_t val) {
while (val >= 0x80) {
*((*dest)++) = static_cast<uint8_t>(0x80 | (val & 0x7F));
val >>= 7;
}
*((*dest)++) = static_cast<uint8_t>(val & 0x7F);
}
// Write a 32-bit signed LEB to {dest}, updating {dest} to point after
// the last uint8_t written. No safety checks.
static void write_i32v(uint8_t** dest, int32_t val) {
if (val >= 0) {
while (val >= 0x40) { // prevent sign extension.
*((*dest)++) = static_cast<uint8_t>(0x80 | (val & 0x7F));
val >>= 7;
}
*((*dest)++) = static_cast<uint8_t>(val & 0xFF);
} else {
while ((val >> 6) != -1) {
*((*dest)++) = static_cast<uint8_t>(0x80 | (val & 0x7F));
val >>= 7;
}
*((*dest)++) = static_cast<uint8_t>(val & 0x7F);
}
}
// Write a 64-bit unsigned LEB to {dest}, updating {dest} to point after
// the last uint8_t written. No safety checks.
static void write_u64v(uint8_t** dest, uint64_t val) {
while (val >= 0x80) {
*((*dest)++) = static_cast<uint8_t>(0x80 | (val & 0x7F));
val >>= 7;
}
*((*dest)++) = static_cast<uint8_t>(val & 0x7F);
}
// Write a 64-bit signed LEB to {dest}, updating {dest} to point after
// the last uint8_t written. No safety checks.
static void write_i64v(uint8_t** dest, int64_t val) {
if (val >= 0) {
while (val >= 0x40) { // prevent sign extension.
*((*dest)++) = static_cast<uint8_t>(0x80 | (val & 0x7F));
val >>= 7;
}
*((*dest)++) = static_cast<uint8_t>(val & 0xFF);
} else {
while ((val >> 6) != -1) {
*((*dest)++) = static_cast<uint8_t>(0x80 | (val & 0x7F));
val >>= 7;
}
*((*dest)++) = static_cast<uint8_t>(val & 0x7F);
}
}
// TODO(titzer): move core logic for decoding LEBs from decoder.h to here.
// Compute the size of {val} if emitted as an LEB32.
static inline size_t sizeof_u32v(size_t val) {
size_t size = 0;
do {
size++;
val = val >> 7;
} while (val > 0);
return size;
}
// Compute the size of {val} if emitted as an LEB32.
static inline size_t sizeof_i32v(int32_t val) {
size_t size = 1;
if (val >= 0) {
while (val >= 0x40) { // prevent sign extension.
size++;
val >>= 7;
}
} else {
while ((val >> 6) != -1) {
size++;
val >>= 7;
}
}
return size;
}
// Compute the size of {val} if emitted as an unsigned LEB64.
static inline size_t sizeof_u64v(uint64_t val) {
size_t size = 0;
do {
size++;
val = val >> 7;
} while (val > 0);
return size;
}
// Compute the size of {val} if emitted as a signed LEB64.
static inline size_t sizeof_i64v(int64_t val) {
size_t size = 1;
if (val >= 0) {
while (val >= 0x40) { // prevent sign extension.
size++;
val >>= 7;
}
} else {
while ((val >> 6) != -1) {
size++;
val >>= 7;
}
}
return size;
}
};
} // namespace wasm
} // namespace internal
} // namespace v8
#endif // V8_WASM_LEB_HELPER_H_
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