pkt-line: introduce struct packet_writer
[git/git.git] / pkt-line.h
1 #ifndef PKTLINE_H
2 #define PKTLINE_H
3
4 #include "git-compat-util.h"
5 #include "strbuf.h"
6
7 /*
8 * Write a packetized stream, where each line is preceded by
9 * its length (including the header) as a 4-byte hex number.
10 * A length of 'zero' means end of stream (and a length of 1-3
11 * would be an error).
12 *
13 * This is all pretty stupid, but we use this packetized line
14 * format to make a streaming format possible without ever
15 * over-running the read buffers. That way we'll never read
16 * into what might be the pack data (which should go to another
17 * process entirely).
18 *
19 * The writing side could use stdio, but since the reading
20 * side can't, we stay with pure read/write interfaces.
21 */
22 void packet_flush(int fd);
23 void packet_delim(int fd);
24 void packet_write_fmt(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
25 void packet_buf_flush(struct strbuf *buf);
26 void packet_buf_delim(struct strbuf *buf);
27 void packet_write(int fd_out, const char *buf, size_t size);
28 void packet_buf_write(struct strbuf *buf, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
29 void packet_buf_write_len(struct strbuf *buf, const char *data, size_t len);
30 int packet_flush_gently(int fd);
31 int packet_write_fmt_gently(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
32 int write_packetized_from_fd(int fd_in, int fd_out);
33 int write_packetized_from_buf(const char *src_in, size_t len, int fd_out);
34
35 /*
36 * Read a packetized line into the buffer, which must be at least size bytes
37 * long. The return value specifies the number of bytes read into the buffer.
38 *
39 * If src_buffer and *src_buffer are not NULL, it should point to a buffer
40 * containing the packet data to parse, of at least *src_len bytes. After the
41 * function returns, src_buf will be incremented and src_len decremented by the
42 * number of bytes consumed.
43 *
44 * If src_buffer (or *src_buffer) is NULL, then data is read from the
45 * descriptor "fd".
46 *
47 * If options does not contain PACKET_READ_GENTLE_ON_EOF, we will die under any
48 * of the following conditions:
49 *
50 * 1. Read error from descriptor.
51 *
52 * 2. Protocol error from the remote (e.g., bogus length characters).
53 *
54 * 3. Receiving a packet larger than "size" bytes.
55 *
56 * 4. Truncated output from the remote (e.g., we expected a packet but got
57 * EOF, or we got a partial packet followed by EOF).
58 *
59 * If options does contain PACKET_READ_GENTLE_ON_EOF, we will not die on
60 * condition 4 (truncated input), but instead return -1. However, we will still
61 * die for the other 3 conditions.
62 *
63 * If options contains PACKET_READ_CHOMP_NEWLINE, a trailing newline (if
64 * present) is removed from the buffer before returning.
65 *
66 * If options contains PACKET_READ_DIE_ON_ERR_PACKET, it dies when it sees an
67 * ERR packet.
68 */
69 #define PACKET_READ_GENTLE_ON_EOF (1u<<0)
70 #define PACKET_READ_CHOMP_NEWLINE (1u<<1)
71 #define PACKET_READ_DIE_ON_ERR_PACKET (1u<<2)
72 int packet_read(int fd, char **src_buffer, size_t *src_len, char
73 *buffer, unsigned size, int options);
74
75 /*
76 * Read a packetized line into a buffer like the 'packet_read()' function but
77 * returns an 'enum packet_read_status' which indicates the status of the read.
78 * The number of bytes read will be assigined to *pktlen if the status of the
79 * read was 'PACKET_READ_NORMAL'.
80 */
81 enum packet_read_status {
82 PACKET_READ_EOF,
83 PACKET_READ_NORMAL,
84 PACKET_READ_FLUSH,
85 PACKET_READ_DELIM,
86 };
87 enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
88 size_t *src_len, char *buffer,
89 unsigned size, int *pktlen,
90 int options);
91
92 /*
93 * Convenience wrapper for packet_read that is not gentle, and sets the
94 * CHOMP_NEWLINE option. The return value is NULL for a flush packet,
95 * and otherwise points to a static buffer (that may be overwritten by
96 * subsequent calls). If the size parameter is not NULL, the length of the
97 * packet is written to it.
98 */
99 char *packet_read_line(int fd, int *size);
100
101 /*
102 * Convenience wrapper for packet_read that sets the PACKET_READ_GENTLE_ON_EOF
103 * and CHOMP_NEWLINE options. The return value specifies the number of bytes
104 * read into the buffer or -1 on truncated input. If the *dst_line parameter
105 * is not NULL it will return NULL for a flush packet or when the number of
106 * bytes copied is zero and otherwise points to a static buffer (that may be
107 * overwritten by subsequent calls). If the size parameter is not NULL, the
108 * length of the packet is written to it.
109 */
110 int packet_read_line_gently(int fd, int *size, char **dst_line);
111
112 /*
113 * Same as packet_read_line, but read from a buf rather than a descriptor;
114 * see packet_read for details on how src_* is used.
115 */
116 char *packet_read_line_buf(char **src_buf, size_t *src_len, int *size);
117
118 /*
119 * Reads a stream of variable sized packets until a flush packet is detected.
120 */
121 ssize_t read_packetized_to_strbuf(int fd_in, struct strbuf *sb_out);
122
123 struct packet_reader {
124 /* source file descriptor */
125 int fd;
126
127 /* source buffer and its size */
128 char *src_buffer;
129 size_t src_len;
130
131 /* buffer that pkt-lines are read into and its size */
132 char *buffer;
133 unsigned buffer_size;
134
135 /* options to be used during reads */
136 int options;
137
138 /* status of the last read */
139 enum packet_read_status status;
140
141 /* length of data read during the last read */
142 int pktlen;
143
144 /* the last line read */
145 const char *line;
146
147 /* indicates if a line has been peeked */
148 int line_peeked;
149 };
150
151 /*
152 * Initialize a 'struct packet_reader' object which is an
153 * abstraction around the 'packet_read_with_status()' function.
154 */
155 extern void packet_reader_init(struct packet_reader *reader, int fd,
156 char *src_buffer, size_t src_len,
157 int options);
158
159 /*
160 * Perform a packet read and return the status of the read.
161 * The values of 'pktlen' and 'line' are updated based on the status of the
162 * read as follows:
163 *
164 * PACKET_READ_ERROR: 'pktlen' is set to '-1' and 'line' is set to NULL
165 * PACKET_READ_NORMAL: 'pktlen' is set to the number of bytes read
166 * 'line' is set to point at the read line
167 * PACKET_READ_FLUSH: 'pktlen' is set to '0' and 'line' is set to NULL
168 */
169 extern enum packet_read_status packet_reader_read(struct packet_reader *reader);
170
171 /*
172 * Peek the next packet line without consuming it and return the status.
173 * The next call to 'packet_reader_read()' will perform a read of the same line
174 * that was peeked, consuming the line.
175 *
176 * Peeking multiple times without calling 'packet_reader_read()' will return
177 * the same result.
178 */
179 extern enum packet_read_status packet_reader_peek(struct packet_reader *reader);
180
181 #define DEFAULT_PACKET_MAX 1000
182 #define LARGE_PACKET_MAX 65520
183 #define LARGE_PACKET_DATA_MAX (LARGE_PACKET_MAX - 4)
184 extern char packet_buffer[LARGE_PACKET_MAX];
185
186 struct packet_writer {
187 int dest_fd;
188 };
189
190 void packet_writer_init(struct packet_writer *writer, int dest_fd);
191
192 /* These functions die upon failure. */
193 __attribute__((format (printf, 2, 3)))
194 void packet_writer_write(struct packet_writer *writer, const char *fmt, ...);
195 __attribute__((format (printf, 2, 3)))
196 void packet_writer_error(struct packet_writer *writer, const char *fmt, ...);
197 void packet_writer_delim(struct packet_writer *writer);
198 void packet_writer_flush(struct packet_writer *writer);
199
200 #endif