Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * pg_get_line.c
4 : : * fgets() with an expansible result buffer
5 : : *
6 : : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
7 : : * Portions Copyright (c) 1994, Regents of the University of California
8 : : *
9 : : *
10 : : * IDENTIFICATION
11 : : * src/common/pg_get_line.c
12 : : *
13 : : *-------------------------------------------------------------------------
14 : : */
15 : : #ifndef FRONTEND
16 : : #include "postgres.h"
17 : : #else
18 : : #include "postgres_fe.h"
19 : : #endif
20 : :
21 : : #include <setjmp.h>
22 : :
23 : : #include "common/string.h"
24 : : #include "lib/stringinfo.h"
25 : :
26 : :
27 : : /*
28 : : * pg_get_line()
29 : : *
30 : : * This is meant to be equivalent to fgets(), except that instead of
31 : : * reading into a caller-supplied, fixed-size buffer, it reads into
32 : : * a palloc'd (in frontend, really malloc'd) string, which is resized
33 : : * as needed to handle indefinitely long input lines. The caller is
34 : : * responsible for pfree'ing the result string when appropriate.
35 : : *
36 : : * As with fgets(), returns NULL if there is a read error or if no
37 : : * characters are available before EOF. The caller can distinguish
38 : : * these cases by checking ferror(stream).
39 : : *
40 : : * Since this is meant to be equivalent to fgets(), the trailing newline
41 : : * (if any) is not stripped. Callers may wish to apply pg_strip_crlf().
42 : : *
43 : : * Note that while I/O errors are reflected back to the caller to be
44 : : * dealt with, an OOM condition for the palloc'd buffer will not be;
45 : : * there'll be an ereport(ERROR) or exit(1) inside stringinfo.c.
46 : : *
47 : : * Also note that the palloc'd buffer is usually a lot longer than
48 : : * strictly necessary, so it may be inadvisable to use this function
49 : : * to collect lots of long-lived data. A less memory-hungry option
50 : : * is to use pg_get_line_buf() or pg_get_line_append() in a loop,
51 : : * then pstrdup() each line.
52 : : *
53 : : * prompt_ctx can optionally be provided to allow this function to be
54 : : * canceled via an existing SIGINT signal handler that will longjmp to the
55 : : * specified place only when *(prompt_ctx->enabled) is true. If canceled,
56 : : * this function returns NULL, and prompt_ctx->canceled is set to true.
57 : : */
58 : : char *
879 tgl@sss.pgh.pa.us 59 :CBC 895 : pg_get_line(FILE *stream, PromptInterruptContext *prompt_ctx)
60 : : {
61 : : StringInfoData buf;
62 : :
1319 63 : 895 : initStringInfo(&buf);
64 : :
879 65 [ - + ]: 895 : if (!pg_get_line_append(stream, &buf, prompt_ctx))
66 : : {
67 : : /* ensure that free() doesn't mess up errno */
1319 tgl@sss.pgh.pa.us 68 :UBC 0 : int save_errno = errno;
69 : :
70 : 0 : pfree(buf.data);
71 : 0 : errno = save_errno;
72 : 0 : return NULL;
73 : : }
74 : :
1316 tgl@sss.pgh.pa.us 75 :CBC 895 : return buf.data;
76 : : }
77 : :
78 : : /*
79 : : * pg_get_line_buf()
80 : : *
81 : : * This has similar behavior to pg_get_line(), and thence to fgets(),
82 : : * except that the collected data is returned in a caller-supplied
83 : : * StringInfo buffer. This is a convenient API for code that just
84 : : * wants to read and process one line at a time, without any artificial
85 : : * limit on line length.
86 : : *
87 : : * Returns true if a line was successfully collected (including the
88 : : * case of a non-newline-terminated line at EOF). Returns false if
89 : : * there was an I/O error or no data was available before EOF.
90 : : * (Check ferror(stream) to distinguish these cases.)
91 : : *
92 : : * In the false-result case, buf is reset to empty.
93 : : */
94 : : bool
1300 95 : 801511 : pg_get_line_buf(FILE *stream, StringInfo buf)
96 : : {
97 : : /* We just need to drop any data from the previous call */
98 : 801511 : resetStringInfo(buf);
879 99 : 801511 : return pg_get_line_append(stream, buf, NULL);
100 : : }
101 : :
102 : : /*
103 : : * pg_get_line_append()
104 : : *
105 : : * This has similar behavior to pg_get_line(), and thence to fgets(),
106 : : * except that the collected data is appended to whatever is in *buf.
107 : : * This is useful in preference to pg_get_line_buf() if the caller wants
108 : : * to merge some lines together, e.g. to implement backslash continuation.
109 : : *
110 : : * Returns true if a line was successfully collected (including the
111 : : * case of a non-newline-terminated line at EOF). Returns false if
112 : : * there was an I/O error or no data was available before EOF.
113 : : * (Check ferror(stream) to distinguish these cases.)
114 : : *
115 : : * In the false-result case, the contents of *buf are logically unmodified,
116 : : * though it's possible that the buffer has been resized.
117 : : *
118 : : * prompt_ctx can optionally be provided to allow this function to be
119 : : * canceled via an existing SIGINT signal handler that will longjmp to the
120 : : * specified place only when *(prompt_ctx->enabled) is true. If canceled,
121 : : * this function returns false, and prompt_ctx->canceled is set to true.
122 : : */
123 : : bool
124 : 961268 : pg_get_line_append(FILE *stream, StringInfo buf,
125 : : PromptInterruptContext *prompt_ctx)
126 : : {
1316 127 : 961268 : int orig_len = buf->len;
128 : :
879 129 [ + + + - ]: 961268 : if (prompt_ctx && sigsetjmp(*((sigjmp_buf *) prompt_ctx->jmpbuf), 1) != 0)
130 : : {
131 : : /* Got here with longjmp */
879 tgl@sss.pgh.pa.us 132 :UBC 0 : prompt_ctx->canceled = true;
133 : : /* Discard any data we collected before detecting error */
134 : 0 : buf->len = orig_len;
135 : 0 : buf->data[orig_len] = '\0';
136 : 0 : return false;
137 : : }
138 : :
139 : : /* Loop until newline or EOF/error */
140 : : for (;;)
879 tgl@sss.pgh.pa.us 141 :CBC 20 : {
142 : : char *res;
143 : :
144 : : /* Enable longjmp while waiting for input */
145 [ + + ]: 961288 : if (prompt_ctx)
146 : 2 : *(prompt_ctx->enabled) = true;
147 : :
148 : : /* Read some data, appending it to whatever we already have */
149 : 961288 : res = fgets(buf->data + buf->len, buf->maxlen - buf->len, stream);
150 : :
151 : : /* Disable longjmp again, then break if fgets failed */
152 [ + + ]: 961288 : if (prompt_ctx)
153 : 2 : *(prompt_ctx->enabled) = false;
154 : :
155 [ + + ]: 961288 : if (res == NULL)
156 : 2513 : break;
157 : :
158 : : /* Got data, so update buf->len */
1316 159 : 958775 : buf->len += strlen(buf->data + buf->len);
160 : :
161 : : /* Done if we have collected a newline */
162 [ + - + + ]: 958775 : if (buf->len > orig_len && buf->data[buf->len - 1] == '\n')
163 : 958755 : return true;
164 : :
165 : : /* Make some more room in the buffer, and loop to read more data */
166 : 20 : enlargeStringInfo(buf, 128);
167 : : }
168 : :
169 : : /* Check for I/O errors and EOF */
170 [ + - + + ]: 2513 : if (ferror(stream) || buf->len == orig_len)
171 : : {
172 : : /* Discard any data we collected before detecting error */
173 : 2494 : buf->len = orig_len;
174 : 2494 : buf->data[orig_len] = '\0';
175 : 2494 : return false;
176 : : }
177 : :
178 : : /* No newline at EOF, but we did collect some data */
1316 tgl@sss.pgh.pa.us 179 :GBC 19 : return true;
180 : : }
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