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 BUTIL_THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_
30#define BUTIL_THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_
31
32#include <stddef.h>
33
34namespace butil {
35namespace snappy {
36
37// A Sink is an interface that consumes a sequence of bytes.
38class Sink {
39 public:
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 // For higher performance, Sink implementations can provide custom
64 // AppendAndTakeOwnership() and GetAppendBufferVariable() methods.
65 // These methods can reduce the number of copies done during
66 // compression/decompression.
67
68 // Append "bytes[0,n-1] to the sink. Takes ownership of "bytes"
69 // and calls the deleter function as (*deleter)(deleter_arg, bytes, n)
70 // to free the buffer. deleter function must be non NULL.
71 //
72 // The default implementation just calls Append and frees "bytes".
73 // Other implementations may avoid a copy while appending the buffer.
74 virtual void AppendAndTakeOwnership(
75 char* bytes, size_t n, void (*deleter)(void*, const char*, size_t),
76 void *deleter_arg);
77
78 // Returns a writable buffer for appending and writes the buffer's capacity to
79 // *allocated_size. Guarantees *allocated_size >= min_size.
80 // May return a pointer to the caller-owned scratch buffer which must have
81 // scratch_size >= min_size.
82 //
83 // The returned buffer is only valid until the next operation
84 // on this ByteSink.
85 //
86 // After writing at most *allocated_size bytes, call Append() with the
87 // pointer returned from this function and the number of bytes written.
88 // Many Append() implementations will avoid copying bytes if this function
89 // returned an internal buffer.
90 //
91 // If the sink implementation allocates or reallocates an internal buffer,
92 // it should use the desired_size_hint if appropriate. If a caller cannot
93 // provide a reasonable guess at the desired capacity, it should set
94 // desired_size_hint = 0.
95 //
96 // If a non-scratch buffer is returned, the caller may only pass
97 // a prefix to it to Append(). That is, it is not correct to pass an
98 // interior pointer to Append().
99 //
100 // The default implementation always returns the scratch buffer.
101 virtual char* GetAppendBufferVariable(
102 size_t min_size, size_t desired_size_hint, char* scratch,
103 size_t scratch_size, size_t* allocated_size);
104
105 private:
106 // No copying
107 Sink(const Sink&);
108 void operator=(const Sink&);
109};
110
111// A Source is an interface that yields a sequence of bytes
112class Source {
113 public:
114 Source() { }
115 virtual ~Source();
116
117 // Return the number of bytes left to read from the source
118 virtual size_t Available() const = 0;
119
120 // Peek at the next flat region of the source. Does not reposition
121 // the source. The returned region is empty iff Available()==0.
122 //
123 // Returns a pointer to the beginning of the region and store its
124 // length in *len.
125 //
126 // The returned region is valid until the next call to Skip() or
127 // until this object is destroyed, whichever occurs first.
128 //
129 // The returned region may be larger than Available() (for example
130 // if this ByteSource is a view on a substring of a larger source).
131 // The caller is responsible for ensuring that it only reads the
132 // Available() bytes.
133 virtual const char* Peek(size_t* len) = 0;
134
135 // Skip the next n bytes. Invalidates any buffer returned by
136 // a previous call to Peek().
137 // REQUIRES: Available() >= n
138 virtual void Skip(size_t n) = 0;
139
140 private:
141 // No copying
142 Source(const Source&);
143 void operator=(const Source&);
144};
145
146// A Source implementation that yields the contents of a flat array
147class ByteArraySource : public Source {
148 public:
149 ByteArraySource(const char* p, size_t n) : ptr_(p), left_(n) { }
150 virtual ~ByteArraySource();
151 size_t Available() const override;
152 const char* Peek(size_t* len) override;
153 void Skip(size_t n) override;
154 private:
155 const char* ptr_;
156 size_t left_;
157};
158
159// A Sink implementation that writes to a flat array without any bound checks.
160class UncheckedByteArraySink : public Sink {
161 public:
162 explicit UncheckedByteArraySink(char* dest) : dest_(dest) { }
163 virtual ~UncheckedByteArraySink();
164 void Append(const char* data, size_t n) override;
165 char* GetAppendBuffer(size_t len, char* scratch) override;
166 char* GetAppendBufferVariable(
167 size_t min_size, size_t desired_size_hint, char* scratch,
168 size_t scratch_size, size_t* allocated_size) override;
169 void AppendAndTakeOwnership(
170 char* bytes, size_t n, void (*deleter)(void*, const char*, size_t),
171 void *deleter_arg) override;
172
173 // Return the current output pointer so that a caller can see how
174 // many bytes were produced.
175 // Note: this is not a Sink method.
176 char* CurrentDestination() const { return dest_; }
177 private:
178 char* dest_;
179};
180
181} // namespace snappy
182} // namespace butil
183
184#endif // BUTIL_THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_
185