Botan: src/filters/buf_filt.cpp Source File

Botan 1.10.17

buf_filt.cpp
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1 /*
2 * Buffered Filter
3 * (C) 1999-2007 Jack Lloyd
4 *
5 * Distributed under the terms of the Botan license
6 */
7
8 #include <botan/buf_filt.h>
9 #include <botan/mem_ops.h>
10 #include <botan/internal/rounding.h>
11 #include <stdexcept>
12
13 namespace Botan {
14
15 /*
16 * Buffered_Filter Constructor
17 */
18 Buffered_Filter::Buffered_Filter(size_t b, size_t f) :
19 main_block_mod(b), final_minimum(f)
20 {
21 if(main_block_mod == 0)
22 throw std::invalid_argument("main_block_mod == 0");
23
24 if(final_minimum > main_block_mod)
25 throw std::invalid_argument("final_minimum > main_block_mod");
26
27 buffer.resize(2 * main_block_mod);
28 buffer_pos = 0;
29 }
30
31 /*
32 * Buffer input into blocks, trying to minimize copying
33 */
34 void Buffered_Filter::write(const byte input[], size_t input_size)
35 {
36 if(!input_size)
37 return;
38
39 if(buffer_pos + input_size >= main_block_mod + final_minimum)
40 {
41 size_t to_copy = std::min<size_t>(buffer.size() - buffer_pos, input_size);
42
43 copy_mem(&buffer[buffer_pos], input, to_copy);
44 buffer_pos += to_copy;
45
46 input += to_copy;
47 input_size -= to_copy;
48
49 size_t total_to_consume =
50 round_down(std::min(buffer_pos,
51 buffer_pos + input_size - final_minimum),
52 main_block_mod);
53
54 buffered_block(&buffer[0], total_to_consume);
55
56 buffer_pos -= total_to_consume;
57
58 copy_mem(&buffer[0], &buffer[total_to_consume], buffer_pos);
59 }
60
61 if(input_size >= final_minimum)
62 {
63 size_t full_blocks = (input_size - final_minimum) / main_block_mod;
64 size_t to_copy = full_blocks * main_block_mod;
65
66 if(to_copy)
67 {
68 buffered_block(input, to_copy);
69
70 input += to_copy;
71 input_size -= to_copy;
72 }
73 }
74
75 copy_mem(&buffer[buffer_pos], input, input_size);
76 buffer_pos += input_size;
77 }
78
79 /*
80 * Finish/flush operation
81 */
82 void Buffered_Filter::end_msg()
83 {
84 if(buffer_pos < final_minimum)
85 throw std::runtime_error("Buffered filter end_msg without enough input");
86
87 size_t spare_blocks = (buffer_pos - final_minimum) / main_block_mod;
88
89 if(spare_blocks)
90 {
91 size_t spare_bytes = main_block_mod * spare_blocks;
92 buffered_block(&buffer[0], spare_bytes);
93 buffered_final(&buffer[spare_bytes], buffer_pos - spare_bytes);
94 }
95 else
96 {
97 buffered_final(&buffer[0], buffer_pos);
98 }
99
100 buffer_pos = 0;
101 }
102
103 }
Botan::MemoryRegion::resize
void resize(size_t n)
Definition: secmem.h:217
Botan::round_down
T round_down(T n, T align_to)
Definition: rounding.h:36
Botan::Buffered_Filter::buffered_final
virtual void buffered_final(const byte input[], size_t length)=0
Botan::Buffered_Filter::end_msg
void end_msg()
Definition: buf_filt.cpp:82
Botan::Buffered_Filter::buffered_block
virtual void buffered_block(const byte input[], size_t length)=0
Botan::Buffered_Filter::write
void write(const byte in[], size_t length)
Definition: buf_filt.cpp:34
Botan::byte
unsigned char byte
Definition: types.h:22
Botan::copy_mem
void copy_mem(T *out, const T *in, size_t n)
Definition: mem_ops.h:22
Botan
Definition: algo_base.h:14
Botan::MemoryRegion::size
size_t size() const
Definition: secmem.h:29
Botan::CT::min
T min(T a, T b)
Definition: ct_utils.h:127
Botan::Buffered_Filter::Buffered_Filter
Buffered_Filter(size_t block_size, size_t final_minimum)
Definition: buf_filt.cpp:18