Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2015 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef V8_WASM_DECODER_H_ |
| 6 | #define V8_WASM_DECODER_H_ |
| 7 | |
| 8 | #include "src/base/smart-pointers.h" |
| 9 | #include "src/flags.h" |
| 10 | #include "src/signature.h" |
| 11 | #include "src/wasm/wasm-result.h" |
| 12 | #include "src/zone-containers.h" |
| 13 | |
| 14 | namespace v8 { |
| 15 | namespace internal { |
| 16 | namespace wasm { |
| 17 | |
| 18 | #if DEBUG |
| 19 | #define TRACE(...) \ |
| 20 | do { \ |
| 21 | if (FLAG_trace_wasm_decoder) PrintF(__VA_ARGS__); \ |
| 22 | } while (false) |
| 23 | #else |
| 24 | #define TRACE(...) |
| 25 | #endif |
| 26 | |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 27 | #if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM) |
| 28 | #define UNALIGNED_ACCESS_OK 1 |
| 29 | #else |
| 30 | #define UNALIGNED_ACCESS_OK 0 |
| 31 | #endif |
| 32 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 33 | // A helper utility to decode bytes, integers, fields, varints, etc, from |
| 34 | // a buffer of bytes. |
| 35 | class Decoder { |
| 36 | public: |
| 37 | Decoder(const byte* start, const byte* end) |
| 38 | : start_(start), |
| 39 | pc_(start), |
| 40 | limit_(end), |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 41 | end_(end), |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 42 | error_pc_(nullptr), |
| 43 | error_pt_(nullptr) {} |
| 44 | |
| 45 | virtual ~Decoder() {} |
| 46 | |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 47 | inline bool check(const byte* base, int offset, int length, const char* msg) { |
| 48 | DCHECK_GE(base, start_); |
| 49 | if ((base + offset + length) > limit_) { |
| 50 | error(base, base + offset, msg); |
| 51 | return false; |
| 52 | } |
| 53 | return true; |
| 54 | } |
| 55 | |
| 56 | // Reads a single 8-bit byte, reporting an error if out of bounds. |
| 57 | inline uint8_t checked_read_u8(const byte* base, int offset, |
| 58 | const char* msg = "expected 1 byte") { |
| 59 | return check(base, offset, 1, msg) ? base[offset] : 0; |
| 60 | } |
| 61 | |
| 62 | // Reads 16-bit word, reporting an error if out of bounds. |
| 63 | inline uint16_t checked_read_u16(const byte* base, int offset, |
| 64 | const char* msg = "expected 2 bytes") { |
| 65 | return check(base, offset, 2, msg) ? read_u16(base + offset) : 0; |
| 66 | } |
| 67 | |
| 68 | // Reads 32-bit word, reporting an error if out of bounds. |
| 69 | inline uint32_t checked_read_u32(const byte* base, int offset, |
| 70 | const char* msg = "expected 4 bytes") { |
| 71 | return check(base, offset, 4, msg) ? read_u32(base + offset) : 0; |
| 72 | } |
| 73 | |
| 74 | // Reads 64-bit word, reporting an error if out of bounds. |
| 75 | inline uint64_t checked_read_u64(const byte* base, int offset, |
| 76 | const char* msg = "expected 8 bytes") { |
| 77 | return check(base, offset, 8, msg) ? read_u64(base + offset) : 0; |
| 78 | } |
| 79 | |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 80 | // Reads a variable-length unsigned integer (little endian). |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 81 | uint32_t checked_read_u32v(const byte* base, int offset, int* length, |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 82 | const char* msg = "expected LEB32") { |
| 83 | return checked_read_leb<uint32_t, false>(base, offset, length, msg); |
| 84 | } |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 85 | |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 86 | // Reads a variable-length signed integer (little endian). |
| 87 | int32_t checked_read_i32v(const byte* base, int offset, int* length, |
| 88 | const char* msg = "expected SLEB32") { |
| 89 | uint32_t result = |
| 90 | checked_read_leb<uint32_t, true>(base, offset, length, msg); |
| 91 | if (*length == 5) return bit_cast<int32_t>(result); |
| 92 | if (*length > 0) { |
| 93 | int shift = 32 - 7 * *length; |
| 94 | // Perform sign extension. |
| 95 | return bit_cast<int32_t>(result << shift) >> shift; |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 96 | } |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 97 | return 0; |
| 98 | } |
| 99 | |
| 100 | // Reads a variable-length unsigned integer (little endian). |
| 101 | uint64_t checked_read_u64v(const byte* base, int offset, int* length, |
| 102 | const char* msg = "expected LEB64") { |
| 103 | return checked_read_leb<uint64_t, false>(base, offset, length, msg); |
| 104 | } |
| 105 | |
| 106 | // Reads a variable-length signed integer (little endian). |
| 107 | int64_t checked_read_i64v(const byte* base, int offset, int* length, |
| 108 | const char* msg = "expected SLEB64") { |
| 109 | uint64_t result = |
| 110 | checked_read_leb<uint64_t, true>(base, offset, length, msg); |
| 111 | if (*length == 10) return bit_cast<int64_t>(result); |
| 112 | if (*length > 0) { |
| 113 | int shift = 64 - 7 * *length; |
| 114 | // Perform sign extension. |
| 115 | return bit_cast<int64_t>(result << shift) >> shift; |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 116 | } |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 117 | return 0; |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 118 | } |
| 119 | |
| 120 | // Reads a single 16-bit unsigned integer (little endian). |
| 121 | inline uint16_t read_u16(const byte* ptr) { |
| 122 | DCHECK(ptr >= start_ && (ptr + 2) <= end_); |
| 123 | #if V8_TARGET_LITTLE_ENDIAN && UNALIGNED_ACCESS_OK |
| 124 | return *reinterpret_cast<const uint16_t*>(ptr); |
| 125 | #else |
| 126 | uint16_t b0 = ptr[0]; |
| 127 | uint16_t b1 = ptr[1]; |
| 128 | return (b1 << 8) | b0; |
| 129 | #endif |
| 130 | } |
| 131 | |
| 132 | // Reads a single 32-bit unsigned integer (little endian). |
| 133 | inline uint32_t read_u32(const byte* ptr) { |
| 134 | DCHECK(ptr >= start_ && (ptr + 4) <= end_); |
| 135 | #if V8_TARGET_LITTLE_ENDIAN && UNALIGNED_ACCESS_OK |
| 136 | return *reinterpret_cast<const uint32_t*>(ptr); |
| 137 | #else |
| 138 | uint32_t b0 = ptr[0]; |
| 139 | uint32_t b1 = ptr[1]; |
| 140 | uint32_t b2 = ptr[2]; |
| 141 | uint32_t b3 = ptr[3]; |
| 142 | return (b3 << 24) | (b2 << 16) | (b1 << 8) | b0; |
| 143 | #endif |
| 144 | } |
| 145 | |
| 146 | // Reads a single 64-bit unsigned integer (little endian). |
| 147 | inline uint64_t read_u64(const byte* ptr) { |
| 148 | DCHECK(ptr >= start_ && (ptr + 8) <= end_); |
| 149 | #if V8_TARGET_LITTLE_ENDIAN && UNALIGNED_ACCESS_OK |
| 150 | return *reinterpret_cast<const uint64_t*>(ptr); |
| 151 | #else |
| 152 | uint32_t b0 = ptr[0]; |
| 153 | uint32_t b1 = ptr[1]; |
| 154 | uint32_t b2 = ptr[2]; |
| 155 | uint32_t b3 = ptr[3]; |
| 156 | uint32_t low = (b3 << 24) | (b2 << 16) | (b1 << 8) | b0; |
| 157 | uint32_t b4 = ptr[4]; |
| 158 | uint32_t b5 = ptr[5]; |
| 159 | uint32_t b6 = ptr[6]; |
| 160 | uint32_t b7 = ptr[7]; |
| 161 | uint64_t high = (b7 << 24) | (b6 << 16) | (b5 << 8) | b4; |
| 162 | return (high << 32) | low; |
| 163 | #endif |
| 164 | } |
| 165 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 166 | // Reads a 8-bit unsigned integer (byte) and advances {pc_}. |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 167 | uint8_t consume_u8(const char* name = nullptr) { |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 168 | TRACE(" +%d %-20s: ", static_cast<int>(pc_ - start_), |
| 169 | name ? name : "uint8_t"); |
| 170 | if (checkAvailable(1)) { |
| 171 | byte val = *(pc_++); |
| 172 | TRACE("%02x = %d\n", val, val); |
| 173 | return val; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 174 | } |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 175 | return traceOffEnd<uint8_t>(); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 176 | } |
| 177 | |
| 178 | // Reads a 16-bit unsigned integer (little endian) and advances {pc_}. |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 179 | uint16_t consume_u16(const char* name = nullptr) { |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 180 | TRACE(" +%d %-20s: ", static_cast<int>(pc_ - start_), |
| 181 | name ? name : "uint16_t"); |
| 182 | if (checkAvailable(2)) { |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 183 | uint16_t val = read_u16(pc_); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 184 | TRACE("%02x %02x = %d\n", pc_[0], pc_[1], val); |
| 185 | pc_ += 2; |
| 186 | return val; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 187 | } |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 188 | return traceOffEnd<uint16_t>(); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 189 | } |
| 190 | |
| 191 | // Reads a single 32-bit unsigned integer (little endian) and advances {pc_}. |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 192 | uint32_t consume_u32(const char* name = nullptr) { |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 193 | TRACE(" +%d %-20s: ", static_cast<int>(pc_ - start_), |
| 194 | name ? name : "uint32_t"); |
| 195 | if (checkAvailable(4)) { |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 196 | uint32_t val = read_u32(pc_); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 197 | TRACE("%02x %02x %02x %02x = %u\n", pc_[0], pc_[1], pc_[2], pc_[3], val); |
| 198 | pc_ += 4; |
| 199 | return val; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 200 | } |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 201 | return traceOffEnd<uint32_t>(); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 202 | } |
| 203 | |
| 204 | // Reads a LEB128 variable-length 32-bit integer and advances {pc_}. |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 205 | uint32_t consume_u32v(int* length, const char* name = nullptr) { |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 206 | TRACE(" +%d %-20s: ", static_cast<int>(pc_ - start_), |
| 207 | name ? name : "varint"); |
| 208 | |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 209 | if (checkAvailable(1)) { |
| 210 | const byte* pos = pc_; |
| 211 | const byte* end = pc_ + 5; |
| 212 | if (end > limit_) end = limit_; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 213 | |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 214 | uint32_t result = 0; |
| 215 | int shift = 0; |
| 216 | byte b = 0; |
| 217 | while (pc_ < end) { |
| 218 | b = *pc_++; |
| 219 | TRACE("%02x ", b); |
| 220 | result = result | ((b & 0x7F) << shift); |
| 221 | if ((b & 0x80) == 0) break; |
| 222 | shift += 7; |
| 223 | } |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 224 | |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 225 | *length = static_cast<int>(pc_ - pos); |
| 226 | if (pc_ == end && (b & 0x80)) { |
| 227 | error(pc_ - 1, "varint too large"); |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 228 | } else if (*length == 0) { |
| 229 | error(pc_, "varint of length 0"); |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 230 | } else { |
| 231 | TRACE("= %u\n", result); |
| 232 | } |
| 233 | return result; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 234 | } |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 235 | return traceOffEnd<uint32_t>(); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 236 | } |
| 237 | |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 238 | // Consume {size} bytes and send them to the bit bucket, advancing {pc_}. |
| 239 | void consume_bytes(int size) { |
| 240 | if (checkAvailable(size)) { |
| 241 | pc_ += size; |
| 242 | } else { |
| 243 | pc_ = limit_; |
| 244 | } |
| 245 | } |
| 246 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 247 | // Check that at least {size} bytes exist between {pc_} and {limit_}. |
| 248 | bool checkAvailable(int size) { |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 249 | intptr_t pc_overflow_value = std::numeric_limits<intptr_t>::max() - size; |
| 250 | if (size < 0 || (intptr_t)pc_ > pc_overflow_value) { |
| 251 | error(pc_, nullptr, "reading %d bytes would underflow/overflow", size); |
| 252 | return false; |
| 253 | } else if (pc_ < start_ || limit_ < (pc_ + size)) { |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 254 | error(pc_, nullptr, "expected %d bytes, fell off end", size); |
| 255 | return false; |
| 256 | } else { |
| 257 | return true; |
| 258 | } |
| 259 | } |
| 260 | |
| 261 | void error(const char* msg) { error(pc_, nullptr, msg); } |
| 262 | |
| 263 | void error(const byte* pc, const char* msg) { error(pc, nullptr, msg); } |
| 264 | |
| 265 | // Sets internal error state. |
| 266 | void error(const byte* pc, const byte* pt, const char* format, ...) { |
| 267 | if (ok()) { |
| 268 | #if DEBUG |
| 269 | if (FLAG_wasm_break_on_decoder_error) { |
| 270 | base::OS::DebugBreak(); |
| 271 | } |
| 272 | #endif |
| 273 | const int kMaxErrorMsg = 256; |
| 274 | char* buffer = new char[kMaxErrorMsg]; |
| 275 | va_list arguments; |
| 276 | va_start(arguments, format); |
| 277 | base::OS::VSNPrintF(buffer, kMaxErrorMsg - 1, format, arguments); |
| 278 | va_end(arguments); |
| 279 | error_msg_.Reset(buffer); |
| 280 | error_pc_ = pc; |
| 281 | error_pt_ = pt; |
| 282 | onFirstError(); |
| 283 | } |
| 284 | } |
| 285 | |
| 286 | // Behavior triggered on first error, overridden in subclasses. |
| 287 | virtual void onFirstError() {} |
| 288 | |
| 289 | // Debugging helper to print bytes up to the end. |
| 290 | template <typename T> |
| 291 | T traceOffEnd() { |
| 292 | T t = 0; |
| 293 | for (const byte* ptr = pc_; ptr < limit_; ptr++) { |
| 294 | TRACE("%02x ", *ptr); |
| 295 | } |
| 296 | TRACE("<end>\n"); |
| 297 | pc_ = limit_; |
| 298 | return t; |
| 299 | } |
| 300 | |
| 301 | // Converts the given value to a {Result}, copying the error if necessary. |
| 302 | template <typename T> |
| 303 | Result<T> toResult(T val) { |
| 304 | Result<T> result; |
| 305 | if (error_pc_) { |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 306 | TRACE("Result error: %s\n", error_msg_.get()); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 307 | result.error_code = kError; |
| 308 | result.start = start_; |
| 309 | result.error_pc = error_pc_; |
| 310 | result.error_pt = error_pt_; |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 311 | // transfer ownership of the error to the result. |
| 312 | result.error_msg.Reset(error_msg_.Detach()); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 313 | } else { |
| 314 | result.error_code = kSuccess; |
| 315 | } |
| 316 | result.val = val; |
| 317 | return result; |
| 318 | } |
| 319 | |
| 320 | // Resets the boundaries of this decoder. |
| 321 | void Reset(const byte* start, const byte* end) { |
| 322 | start_ = start; |
| 323 | pc_ = start; |
| 324 | limit_ = end; |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 325 | end_ = end; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 326 | error_pc_ = nullptr; |
| 327 | error_pt_ = nullptr; |
| 328 | error_msg_.Reset(nullptr); |
| 329 | } |
| 330 | |
| 331 | bool ok() const { return error_pc_ == nullptr; } |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 332 | bool failed() const { return !error_msg_.is_empty(); } |
| 333 | bool more() const { return pc_ < limit_; } |
| 334 | |
| 335 | const byte* start() { return start_; } |
| 336 | const byte* pc() { return pc_; } |
| 337 | uint32_t pc_offset() { return static_cast<uint32_t>(pc_ - start_); } |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 338 | |
| 339 | protected: |
| 340 | const byte* start_; |
| 341 | const byte* pc_; |
| 342 | const byte* limit_; |
Ben Murdoch | 097c5b2 | 2016-05-18 11:27:45 +0100 | [diff] [blame] | 343 | const byte* end_; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 344 | const byte* error_pc_; |
| 345 | const byte* error_pt_; |
| 346 | base::SmartArrayPointer<char> error_msg_; |
Ben Murdoch | da12d29 | 2016-06-02 14:46:10 +0100 | [diff] [blame^] | 347 | |
| 348 | private: |
| 349 | template <typename IntType, bool is_signed> |
| 350 | IntType checked_read_leb(const byte* base, int offset, int* length, |
| 351 | const char* msg) { |
| 352 | if (!check(base, offset, 1, msg)) { |
| 353 | *length = 0; |
| 354 | return 0; |
| 355 | } |
| 356 | |
| 357 | const int kMaxLength = (sizeof(IntType) * 8 + 6) / 7; |
| 358 | const byte* ptr = base + offset; |
| 359 | const byte* end = ptr + kMaxLength; |
| 360 | if (end > limit_) end = limit_; |
| 361 | int shift = 0; |
| 362 | byte b = 0; |
| 363 | IntType result = 0; |
| 364 | while (ptr < end) { |
| 365 | b = *ptr++; |
| 366 | result = result | (static_cast<IntType>(b & 0x7F) << shift); |
| 367 | if ((b & 0x80) == 0) break; |
| 368 | shift += 7; |
| 369 | } |
| 370 | DCHECK_LE(ptr - (base + offset), kMaxLength); |
| 371 | *length = static_cast<int>(ptr - (base + offset)); |
| 372 | if (ptr == end) { |
| 373 | // Check there are no bits set beyond the bitwidth of {IntType}. |
| 374 | const int kExtraBits = (1 + kMaxLength * 7) - (sizeof(IntType) * 8); |
| 375 | const byte kExtraBitsMask = |
| 376 | static_cast<byte>((0xFF << (8 - kExtraBits)) & 0xFF); |
| 377 | int extra_bits_value; |
| 378 | if (is_signed) { |
| 379 | // A signed-LEB128 must sign-extend the final byte, excluding its |
| 380 | // most-signifcant bit. e.g. for a 32-bit LEB128: |
| 381 | // kExtraBits = 4 |
| 382 | // kExtraBitsMask = 0xf0 |
| 383 | // If b is 0x0f, the value is negative, so extra_bits_value is 0x70. |
| 384 | // If b is 0x03, the value is positive, so extra_bits_value is 0x00. |
| 385 | extra_bits_value = (static_cast<int8_t>(b << kExtraBits) >> 8) & |
| 386 | kExtraBitsMask & ~0x80; |
| 387 | } else { |
| 388 | extra_bits_value = 0; |
| 389 | } |
| 390 | if (*length == kMaxLength && (b & kExtraBitsMask) != extra_bits_value) { |
| 391 | error(base, ptr, "extra bits in varint"); |
| 392 | return 0; |
| 393 | } |
| 394 | if ((b & 0x80) != 0) { |
| 395 | error(base, ptr, msg); |
| 396 | return 0; |
| 397 | } |
| 398 | } |
| 399 | return result; |
| 400 | } |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 401 | }; |
| 402 | |
| 403 | #undef TRACE |
| 404 | } // namespace wasm |
| 405 | } // namespace internal |
| 406 | } // namespace v8 |
| 407 | |
| 408 | #endif // V8_WASM_DECODER_H_ |