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 UTIL_SNAPPY_SNAPPY_SINKSOURCE_H_ 30 #define UTIL_SNAPPY_SNAPPY_SINKSOURCE_H_ 31 32 #include <stddef.h> 33 34 35 namespace snappy { 36 37 // A Sink is an interface that consumes a sequence of bytes. 38 class Sink { 39 public: Sink()40 Sink() { } 41 virtual ~Sink(); 42 43 // Append "bytes[0,n-1]" to this. 44 virtual void Append(const char* bytes, size_t n) = 0; 45 46 // Returns a writable buffer of the specified length for appending. 47 // May return a pointer to the caller-owned scratch buffer which 48 // must have at least the indicated length. The returned buffer is 49 // only valid until the next operation on this Sink. 50 // 51 // After writing at most "length" bytes, call Append() with the 52 // pointer returned from this function and the number of bytes 53 // written. Many Append() implementations will avoid copying 54 // bytes if this function returned an internal buffer. 55 // 56 // If a non-scratch buffer is returned, the caller may only pass a 57 // prefix of it to Append(). That is, it is not correct to pass an 58 // interior pointer of the returned array to Append(). 59 // 60 // The default implementation always returns the scratch buffer. 61 virtual char* GetAppendBuffer(size_t length, char* scratch); 62 63 64 private: 65 // No copying 66 Sink(const Sink&); 67 void operator=(const Sink&); 68 }; 69 70 // A Source is an interface that yields a sequence of bytes 71 class Source { 72 public: Source()73 Source() { } 74 virtual ~Source(); 75 76 // Return the number of bytes left to read from the source 77 virtual size_t Available() const = 0; 78 79 // Peek at the next flat region of the source. Does not reposition 80 // the source. The returned region is empty iff Available()==0. 81 // 82 // Returns a pointer to the beginning of the region and store its 83 // length in *len. 84 // 85 // The returned region is valid until the next call to Skip() or 86 // until this object is destroyed, whichever occurs first. 87 // 88 // The returned region may be larger than Available() (for example 89 // if this ByteSource is a view on a substring of a larger source). 90 // The caller is responsible for ensuring that it only reads the 91 // Available() bytes. 92 virtual const char* Peek(size_t* len) = 0; 93 94 // Skip the next n bytes. Invalidates any buffer returned by 95 // a previous call to Peek(). 96 // REQUIRES: Available() >= n 97 virtual void Skip(size_t n) = 0; 98 99 private: 100 // No copying 101 Source(const Source&); 102 void operator=(const Source&); 103 }; 104 105 // A Source implementation that yields the contents of a flat array 106 class ByteArraySource : public Source { 107 public: ByteArraySource(const char * p,size_t n)108 ByteArraySource(const char* p, size_t n) : ptr_(p), left_(n) { } 109 virtual ~ByteArraySource(); 110 virtual size_t Available() const; 111 virtual const char* Peek(size_t* len); 112 virtual void Skip(size_t n); 113 private: 114 const char* ptr_; 115 size_t left_; 116 }; 117 118 // A Sink implementation that writes to a flat array without any bound checks. 119 class UncheckedByteArraySink : public Sink { 120 public: UncheckedByteArraySink(char * dest)121 explicit UncheckedByteArraySink(char* dest) : dest_(dest) { } 122 virtual ~UncheckedByteArraySink(); 123 virtual void Append(const char* data, size_t n); 124 virtual char* GetAppendBuffer(size_t len, char* scratch); 125 126 // Return the current output pointer so that a caller can see how 127 // many bytes were produced. 128 // Note: this is not a Sink method. CurrentDestination()129 char* CurrentDestination() const { return dest_; } 130 private: 131 char* dest_; 132 }; 133 134 135 } 136 137 #endif // UTIL_SNAPPY_SNAPPY_SINKSOURCE_H_ 138