1 /*
2 * Copyright 2009-2015 MongoDB, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 /* Include Python.h so we can set Python's error indicator. */
18 #define PY_SSIZE_T_CLEAN
19 #include "Python.h"
20
21 #include <stdlib.h>
22 #include <string.h>
23
24 #include "buffer.h"
25
26 #define INITIAL_BUFFER_SIZE 256
27
28 struct buffer {
29 char* buffer;
30 int size;
31 int position;
32 };
33
34 /* Set Python's error indicator to MemoryError.
35 * Called after allocation failures. */
set_memory_error(void)36 static void set_memory_error(void) {
37 PyErr_NoMemory();
38 }
39
40 /* Allocate and return a new buffer.
41 * Return NULL and sets MemoryError on allocation failure. */
buffer_new(void)42 buffer_t buffer_new(void) {
43 buffer_t buffer;
44 buffer = (buffer_t)malloc(sizeof(struct buffer));
45 if (buffer == NULL) {
46 set_memory_error();
47 return NULL;
48 }
49
50 buffer->size = INITIAL_BUFFER_SIZE;
51 buffer->position = 0;
52 buffer->buffer = (char*)malloc(sizeof(char) * INITIAL_BUFFER_SIZE);
53 if (buffer->buffer == NULL) {
54 free(buffer);
55 set_memory_error();
56 return NULL;
57 }
58
59 return buffer;
60 }
61
62 /* Free the memory allocated for `buffer`.
63 * Return non-zero on failure. */
buffer_free(buffer_t buffer)64 int buffer_free(buffer_t buffer) {
65 if (buffer == NULL) {
66 return 1;
67 }
68 /* Buffer will be NULL when buffer_grow fails. */
69 if (buffer->buffer != NULL) {
70 free(buffer->buffer);
71 }
72 free(buffer);
73 return 0;
74 }
75
76 /* Grow `buffer` to at least `min_length`.
77 * Return non-zero and sets MemoryError on allocation failure. */
buffer_grow(buffer_t buffer,int min_length)78 static int buffer_grow(buffer_t buffer, int min_length) {
79 int old_size = 0;
80 int size = buffer->size;
81 char* old_buffer = buffer->buffer;
82 if (size >= min_length) {
83 return 0;
84 }
85 while (size < min_length) {
86 old_size = size;
87 size *= 2;
88 if (size <= old_size) {
89 /* Size did not increase. Could be an overflow
90 * or size < 1. Just go with min_length. */
91 size = min_length;
92 }
93 }
94 buffer->buffer = (char*)realloc(buffer->buffer, sizeof(char) * size);
95 if (buffer->buffer == NULL) {
96 free(old_buffer);
97 set_memory_error();
98 return 1;
99 }
100 buffer->size = size;
101 return 0;
102 }
103
104 /* Assure that `buffer` has at least `size` free bytes (and grow if needed).
105 * Return non-zero and sets MemoryError on allocation failure.
106 * Return non-zero and sets ValueError if `size` would exceed 2GiB. */
buffer_assure_space(buffer_t buffer,int size)107 static int buffer_assure_space(buffer_t buffer, int size) {
108 int new_size = buffer->position + size;
109 /* Check for overflow. */
110 if (new_size < buffer->position) {
111 PyErr_SetString(PyExc_ValueError,
112 "Document would overflow BSON size limit");
113 return 1;
114 }
115
116 if (new_size <= buffer->size) {
117 return 0;
118 }
119 return buffer_grow(buffer, new_size);
120 }
121
122 /* Save `size` bytes from the current position in `buffer` (and grow if needed).
123 * Return offset for writing, or -1 on failure.
124 * Sets MemoryError or ValueError on failure. */
buffer_save_space(buffer_t buffer,int size)125 buffer_position buffer_save_space(buffer_t buffer, int size) {
126 int position = buffer->position;
127 if (buffer_assure_space(buffer, size) != 0) {
128 return -1;
129 }
130 buffer->position += size;
131 return position;
132 }
133
134 /* Write `size` bytes from `data` to `buffer` (and grow if needed).
135 * Return non-zero on failure.
136 * Sets MemoryError or ValueError on failure. */
buffer_write(buffer_t buffer,const char * data,int size)137 int buffer_write(buffer_t buffer, const char* data, int size) {
138 if (buffer_assure_space(buffer, size) != 0) {
139 return 1;
140 }
141
142 memcpy(buffer->buffer + buffer->position, data, size);
143 buffer->position += size;
144 return 0;
145 }
146
buffer_get_position(buffer_t buffer)147 int buffer_get_position(buffer_t buffer) {
148 return buffer->position;
149 }
150
buffer_get_buffer(buffer_t buffer)151 char* buffer_get_buffer(buffer_t buffer) {
152 return buffer->buffer;
153 }
154
buffer_update_position(buffer_t buffer,buffer_position new_position)155 void buffer_update_position(buffer_t buffer, buffer_position new_position) {
156 buffer->position = new_position;
157 }
158