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Diffstat (limited to 'lib/read-file.c')
| -rw-r--r-- | lib/read-file.c | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/lib/read-file.c b/lib/read-file.c new file mode 100644 index 0000000..1e62085 --- /dev/null +++ b/lib/read-file.c @@ -0,0 +1,216 @@ +/* read-file.c -- read file contents into a string + Copyright (C) 2006, 2009-2023 Free Software Foundation, Inc. + Written by Simon Josefsson and Bruno Haible. + + This file is free software: you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License as + published by the Free Software Foundation; either version 2.1 of the + License, or (at your option) any later version. + + This file is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +#include <config.h> + +#include "read-file.h" + +/* Get fstat. */ +#include <sys/stat.h> + +/* Get ftello. */ +#include <stdio.h> + +/* Get PTRDIFF_MAX. */ +#include <stdint.h> + +/* Get malloc, realloc, free. */ +#include <stdlib.h> + +/* Get memcpy, memset_explicit. */ +#include <string.h> + +/* Get errno. */ +#include <errno.h> + +/* Read a STREAM and return a newly allocated string with the content, + and set *LENGTH to the length of the string. The string is + zero-terminated, but the terminating zero byte is not counted in + *LENGTH. On errors, *LENGTH is undefined, errno preserves the + values set by system functions (if any), and NULL is returned. + + If the RF_SENSITIVE flag is set in FLAGS: + - You should control the buffering of STREAM using 'setvbuf'. Either + clear the buffer of STREAM after closing it, or disable buffering of + STREAM before calling this function. + - The memory buffer internally allocated will be cleared upon failure. */ +char * +fread_file (FILE *stream, int flags, size_t *length) +{ + char *buf = NULL; + size_t alloc = BUFSIZ; + + /* For a regular file, allocate a buffer that has exactly the right + size. This avoids the need to do dynamic reallocations later. */ + { + struct stat st; + + if (fstat (fileno (stream), &st) >= 0 && S_ISREG (st.st_mode)) + { + off_t pos = ftello (stream); + + if (pos >= 0 && pos < st.st_size) + { + off_t alloc_off = st.st_size - pos; + + /* '1' below, accounts for the trailing NUL. */ + if (PTRDIFF_MAX - 1 < alloc_off) + { + errno = ENOMEM; + return NULL; + } + + alloc = alloc_off + 1; + } + } + } + + if (!(buf = malloc (alloc))) + return NULL; /* errno is ENOMEM. */ + + { + size_t size = 0; /* number of bytes read so far */ + int save_errno; + + for (;;) + { + /* This reads 1 more than the size of a regular file + so that we get eof immediately. */ + size_t requested = alloc - size; + size_t count = fread (buf + size, 1, requested, stream); + size += count; + + if (count != requested) + { + save_errno = errno; + if (ferror (stream)) + break; + + /* Shrink the allocated memory if possible. */ + if (size < alloc - 1) + { + if (flags & RF_SENSITIVE) + { + char *smaller_buf = malloc (size + 1); + if (smaller_buf == NULL) + memset_explicit (buf + size, 0, alloc - size); + else + { + memcpy (smaller_buf, buf, size); + memset_explicit (buf, 0, alloc); + free (buf); + buf = smaller_buf; + } + } + else + { + char *smaller_buf = realloc (buf, size + 1); + if (smaller_buf != NULL) + buf = smaller_buf; + } + } + + buf[size] = '\0'; + *length = size; + return buf; + } + + { + char *new_buf; + size_t save_alloc = alloc; + + if (alloc == PTRDIFF_MAX) + { + save_errno = ENOMEM; + break; + } + + if (alloc < PTRDIFF_MAX - alloc / 2) + alloc = alloc + alloc / 2; + else + alloc = PTRDIFF_MAX; + + if (flags & RF_SENSITIVE) + { + new_buf = malloc (alloc); + if (!new_buf) + { + /* BUF should be cleared below after the loop. */ + save_errno = errno; + break; + } + memcpy (new_buf, buf, save_alloc); + memset_explicit (buf, 0, save_alloc); + free (buf); + } + else if (!(new_buf = realloc (buf, alloc))) + { + save_errno = errno; + break; + } + + buf = new_buf; + } + } + + if (flags & RF_SENSITIVE) + memset_explicit (buf, 0, alloc); + + free (buf); + errno = save_errno; + return NULL; + } +} + +/* Open and read the contents of FILENAME, and return a newly + allocated string with the content, and set *LENGTH to the length of + the string. The string is zero-terminated, but the terminating + zero byte is not counted in *LENGTH. On errors, *LENGTH is + undefined, errno preserves the values set by system functions (if + any), and NULL is returned. + + If the RF_BINARY flag is set in FLAGS, the file is opened in binary + mode. If the RF_SENSITIVE flag is set in FLAGS, the memory buffer + internally allocated will be cleared upon failure. */ +char * +read_file (const char *filename, int flags, size_t *length) +{ + const char *mode = (flags & RF_BINARY) ? "rbe" : "re"; + FILE *stream = fopen (filename, mode); + char *out; + + if (!stream) + return NULL; + + if (flags & RF_SENSITIVE) + setvbuf (stream, NULL, _IONBF, 0); + + out = fread_file (stream, flags, length); + + if (fclose (stream) != 0) + { + if (out) + { + if (flags & RF_SENSITIVE) + memset_explicit (out, 0, *length); + free (out); + } + return NULL; + } + + return out; +} |