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+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Endian-neutral encoding:
+// * Fixed-length numbers are encoded with least-significant byte first
+// * In addition we support variable length "varint" encoding
+// * Strings are encoded prefixed by their length in varint format
+
+#ifndef STORAGE_LEVELDB_UTIL_CODING_H_
+#define STORAGE_LEVELDB_UTIL_CODING_H_
+
+#include <stdint.h>
+#include <string.h>
+#include <string>
+#include "leveldb/slice.h"
+#include "port/port.h"
+
+namespace leveldb {
+
+// Standard Put... routines append to a string
+extern void PutFixed32(std::string* dst, uint32_t value);
+extern void PutFixed64(std::string* dst, uint64_t value);
+extern void PutVarint32(std::string* dst, uint32_t value);
+extern void PutVarint64(std::string* dst, uint64_t value);
+extern void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
+
+// Standard Get... routines parse a value from the beginning of a Slice
+// and advance the slice past the parsed value.
+extern bool GetVarint32(Slice* input, uint32_t* value);
+extern bool GetVarint64(Slice* input, uint64_t* value);
+extern bool GetLengthPrefixedSlice(Slice* input, Slice* result);
+
+// Pointer-based variants of GetVarint... These either store a value
+// in *v and return a pointer just past the parsed value, or return
+// NULL on error. These routines only look at bytes in the range
+// [p..limit-1]
+extern const char* GetVarint32Ptr(const char* p,const char* limit, uint32_t* v);
+extern const char* GetVarint64Ptr(const char* p,const char* limit, uint64_t* v);
+
+// Returns the length of the varint32 or varint64 encoding of "v"
+extern int VarintLength(uint64_t v);
+
+// Lower-level versions of Put... that write directly into a character buffer
+// REQUIRES: dst has enough space for the value being written
+extern void EncodeFixed32(char* dst, uint32_t value);
+extern void EncodeFixed64(char* dst, uint64_t value);
+
+// Lower-level versions of Put... that write directly into a character buffer
+// and return a pointer just past the last byte written.
+// REQUIRES: dst has enough space for the value being written
+extern char* EncodeVarint32(char* dst, uint32_t value);
+extern char* EncodeVarint64(char* dst, uint64_t value);
+
+// Lower-level versions of Get... that read directly from a character buffer
+// without any bounds checking.
+
+inline uint32_t DecodeFixed32(const char* ptr) {
+ if (port::kLittleEndian) {
+ // Load the raw bytes
+ uint32_t result;
+ memcpy(&result, ptr, sizeof(result)); // gcc optimizes this to a plain load
+ return result;
+ } else {
+ return ((static_cast<uint32_t>(static_cast<unsigned char>(ptr[0])))
+ | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[1])) << 8)
+ | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[2])) << 16)
+ | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[3])) << 24));
+ }
+}
+
+inline uint64_t DecodeFixed64(const char* ptr) {
+ if (port::kLittleEndian) {
+ // Load the raw bytes
+ uint64_t result;
+ memcpy(&result, ptr, sizeof(result)); // gcc optimizes this to a plain load
+ return result;
+ } else {
+ uint64_t lo = DecodeFixed32(ptr);
+ uint64_t hi = DecodeFixed32(ptr + 4);
+ return (hi << 32) | lo;
+ }
+}
+
+// Internal routine for use by fallback path of GetVarint32Ptr
+extern const char* GetVarint32PtrFallback(const char* p,
+ const char* limit,
+ uint32_t* value);
+inline const char* GetVarint32Ptr(const char* p,
+ const char* limit,
+ uint32_t* value) {
+ if (p < limit) {
+ uint32_t result = *(reinterpret_cast<const unsigned char*>(p));
+ if ((result & 128) == 0) {
+ *value = result;
+ return p + 1;
+ }
+ }
+ return GetVarint32PtrFallback(p, limit, value);
+}
+
+} // namespace leveldb
+
+#endif // STORAGE_LEVELDB_UTIL_CODING_H_