snappy-sinksource.h (7265B)
1 // Copyright 2011 Google Inc. All Rights Reserved. 2 // 3 // Redistribution and use in source and binary forms, with or without 4 // modification, are permitted provided that the following conditions are 5 // met: 6 // 7 // * Redistributions of source code must retain the above copyright 8 // notice, this list of conditions and the following disclaimer. 9 // * Redistributions in binary form must reproduce the above 10 // copyright notice, this list of conditions and the following disclaimer 11 // in the documentation and/or other materials provided with the 12 // distribution. 13 // * Neither the name of Google Inc. nor the names of its 14 // contributors may be used to endorse or promote products derived from 15 // this software without specific prior written permission. 16 // 17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 20 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 21 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 22 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 23 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 29 #ifndef THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_ 30 #define THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_ 31 32 #include <stddef.h> 33 34 namespace snappy { 35 36 // A Sink is an interface that consumes a sequence of bytes. 37 class Sink { 38 public: 39 Sink() { } 40 virtual ~Sink(); 41 42 // Append "bytes[0,n-1]" to this. 43 virtual void Append(const char* bytes, size_t n) = 0; 44 45 // Returns a writable buffer of the specified length for appending. 46 // May return a pointer to the caller-owned scratch buffer which 47 // must have at least the indicated length. The returned buffer is 48 // only valid until the next operation on this Sink. 49 // 50 // After writing at most "length" bytes, call Append() with the 51 // pointer returned from this function and the number of bytes 52 // written. Many Append() implementations will avoid copying 53 // bytes if this function returned an internal buffer. 54 // 55 // If a non-scratch buffer is returned, the caller may only pass a 56 // prefix of it to Append(). That is, it is not correct to pass an 57 // interior pointer of the returned array to Append(). 58 // 59 // The default implementation always returns the scratch buffer. 60 virtual char* GetAppendBuffer(size_t length, char* scratch); 61 62 // For higher performance, Sink implementations can provide custom 63 // AppendAndTakeOwnership() and GetAppendBufferVariable() methods. 64 // These methods can reduce the number of copies done during 65 // compression/decompression. 66 67 // Append "bytes[0,n-1] to the sink. Takes ownership of "bytes" 68 // and calls the deleter function as (*deleter)(deleter_arg, bytes, n) 69 // to free the buffer. deleter function must be non NULL. 70 // 71 // The default implementation just calls Append and frees "bytes". 72 // Other implementations may avoid a copy while appending the buffer. 73 virtual void AppendAndTakeOwnership( 74 char* bytes, size_t n, void (*deleter)(void*, const char*, size_t), 75 void *deleter_arg); 76 77 // Returns a writable buffer for appending and writes the buffer's capacity to 78 // *allocated_size. Guarantees *allocated_size >= min_size. 79 // May return a pointer to the caller-owned scratch buffer which must have 80 // scratch_size >= min_size. 81 // 82 // The returned buffer is only valid until the next operation 83 // on this ByteSink. 84 // 85 // After writing at most *allocated_size bytes, call Append() with the 86 // pointer returned from this function and the number of bytes written. 87 // Many Append() implementations will avoid copying bytes if this function 88 // returned an internal buffer. 89 // 90 // If the sink implementation allocates or reallocates an internal buffer, 91 // it should use the desired_size_hint if appropriate. If a caller cannot 92 // provide a reasonable guess at the desired capacity, it should set 93 // desired_size_hint = 0. 94 // 95 // If a non-scratch buffer is returned, the caller may only pass 96 // a prefix to it to Append(). That is, it is not correct to pass an 97 // interior pointer to Append(). 98 // 99 // The default implementation always returns the scratch buffer. 100 virtual char* GetAppendBufferVariable( 101 size_t min_size, size_t desired_size_hint, char* scratch, 102 size_t scratch_size, size_t* allocated_size); 103 104 private: 105 // No copying 106 Sink(const Sink&); 107 void operator=(const Sink&); 108 }; 109 110 // A Source is an interface that yields a sequence of bytes 111 class Source { 112 public: 113 Source() { } 114 virtual ~Source(); 115 116 // Return the number of bytes left to read from the source 117 virtual size_t Available() const = 0; 118 119 // Peek at the next flat region of the source. Does not reposition 120 // the source. The returned region is empty iff Available()==0. 121 // 122 // Returns a pointer to the beginning of the region and store its 123 // length in *len. 124 // 125 // The returned region is valid until the next call to Skip() or 126 // until this object is destroyed, whichever occurs first. 127 // 128 // The returned region may be larger than Available() (for example 129 // if this ByteSource is a view on a substring of a larger source). 130 // The caller is responsible for ensuring that it only reads the 131 // Available() bytes. 132 virtual const char* Peek(size_t* len) = 0; 133 134 // Skip the next n bytes. Invalidates any buffer returned by 135 // a previous call to Peek(). 136 // REQUIRES: Available() >= n 137 virtual void Skip(size_t n) = 0; 138 139 private: 140 // No copying 141 Source(const Source&); 142 void operator=(const Source&); 143 }; 144 145 // A Source implementation that yields the contents of a flat array 146 class ByteArraySource : public Source { 147 public: 148 ByteArraySource(const char* p, size_t n) : ptr_(p), left_(n) { } 149 ~ByteArraySource() override; 150 size_t Available() const override; 151 const char* Peek(size_t* len) override; 152 void Skip(size_t n) override; 153 private: 154 const char* ptr_; 155 size_t left_; 156 }; 157 158 // A Sink implementation that writes to a flat array without any bound checks. 159 class UncheckedByteArraySink : public Sink { 160 public: 161 explicit UncheckedByteArraySink(char* dest) : dest_(dest) { } 162 ~UncheckedByteArraySink() override; 163 void Append(const char* data, size_t n) override; 164 char* GetAppendBuffer(size_t len, char* scratch) override; 165 char* GetAppendBufferVariable( 166 size_t min_size, size_t desired_size_hint, char* scratch, 167 size_t scratch_size, size_t* allocated_size) override; 168 void AppendAndTakeOwnership( 169 char* bytes, size_t n, void (*deleter)(void*, const char*, size_t), 170 void *deleter_arg) override; 171 172 // Return the current output pointer so that a caller can see how 173 // many bytes were produced. 174 // Note: this is not a Sink method. 175 char* CurrentDestination() const { return dest_; } 176 private: 177 char* dest_; 178 }; 179 180 } // namespace snappy 181 182 #endif // THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_