diff options
Diffstat (limited to 'lib/getndelim2.c')
| -rw-r--r-- | lib/getndelim2.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/lib/getndelim2.c b/lib/getndelim2.c new file mode 100644 index 0000000..2611bc2 --- /dev/null +++ b/lib/getndelim2.c @@ -0,0 +1,217 @@ +/* getndelim2 - Read a line from a stream, stopping at one of 2 delimiters, + with bounded memory allocation. + + Copyright (C) 1993, 1996-1998, 2000, 2003-2004, 2006, 2008-2022 Free + Software Foundation, Inc. + + 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/>. */ + +/* Originally written by Jan Brittenson, bson@gnu.ai.mit.edu. */ + +#include <config.h> + +#include "getndelim2.h" + +#include <stdbool.h> +#include <stddef.h> +#include <stdlib.h> +#include <string.h> + +#if USE_UNLOCKED_IO +# include "unlocked-io.h" +#endif +#if !HAVE_FLOCKFILE +# undef flockfile +# define flockfile(x) ((void) 0) +#endif +#if !HAVE_FUNLOCKFILE +# undef funlockfile +# define funlockfile(x) ((void) 0) +#endif + +#include <limits.h> +#include <stdint.h> + +#include "freadptr.h" +#include "freadseek.h" +#include "memchr2.h" + +#ifndef SSIZE_MAX +# define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2)) +#endif + +/* Use this to suppress gcc's "...may be used before initialized" warnings. */ +#if defined GCC_LINT || defined lint +# define IF_LINT(Code) Code +#else +# define IF_LINT(Code) /* empty */ +#endif + +/* The maximum value that getndelim2 can return without suffering from + overflow problems, either internally (because of pointer + subtraction overflow) or due to the API (because of ssize_t). */ +#define GETNDELIM2_MAXIMUM (PTRDIFF_MAX < SSIZE_MAX ? PTRDIFF_MAX : SSIZE_MAX) + +/* Try to add at least this many bytes when extending the buffer. + MIN_CHUNK must be no greater than GETNDELIM2_MAXIMUM. */ +#define MIN_CHUNK 64 + +ssize_t +getndelim2 (char **lineptr, size_t *linesize, size_t offset, size_t nmax, + int delim1, int delim2, FILE *stream) +{ + size_t nbytes_avail; /* Allocated but unused bytes in *LINEPTR. */ + char *read_pos; /* Where we're reading into *LINEPTR. */ + ssize_t bytes_stored = -1; + char *ptr = *lineptr; + size_t size = *linesize; + bool found_delimiter; + + if (!ptr) + { + size = nmax < MIN_CHUNK ? nmax : MIN_CHUNK; + ptr = malloc (size); + if (!ptr) + return -1; + } + + if (size < offset) + goto done; + + nbytes_avail = size - offset; + read_pos = ptr + offset; + + if (nbytes_avail == 0 && nmax <= size) + goto done; + + /* Normalize delimiters, since memchr2 doesn't handle EOF. */ + if (delim1 == EOF) + delim1 = delim2; + else if (delim2 == EOF) + delim2 = delim1; + + flockfile (stream); + + found_delimiter = false; + do + { + /* Here always ptr + size == read_pos + nbytes_avail. + Also nbytes_avail > 0 || size < nmax. */ + + int c IF_LINT (= 0); + const char *buffer; + size_t buffer_len; + + buffer = freadptr (stream, &buffer_len); + if (buffer) + { + if (delim1 != EOF) + { + const char *end = memchr2 (buffer, delim1, delim2, buffer_len); + if (end) + { + buffer_len = end - buffer + 1; + found_delimiter = true; + } + } + } + else + { + c = getc (stream); + if (c == EOF) + { + /* Return partial line, if any. */ + if (read_pos == ptr) + goto unlock_done; + else + break; + } + if (c == delim1 || c == delim2) + found_delimiter = true; + buffer_len = 1; + } + + /* We always want at least one byte left in the buffer, since we + always (unless we get an error while reading the first byte) + NUL-terminate the line buffer. */ + + if (nbytes_avail < buffer_len + 1 && size < nmax) + { + /* Grow size proportionally, not linearly, to avoid O(n^2) + running time. */ + size_t newsize = size < MIN_CHUNK ? size + MIN_CHUNK : 2 * size; + char *newptr; + + /* Increase newsize so that it becomes + >= (read_pos - ptr) + buffer_len. */ + if (newsize - (read_pos - ptr) < buffer_len + 1) + newsize = (read_pos - ptr) + buffer_len + 1; + /* Respect nmax. This handles possible integer overflow. */ + if (! (size < newsize && newsize <= nmax)) + newsize = nmax; + + if (GETNDELIM2_MAXIMUM < newsize - offset) + { + size_t newsizemax = offset + GETNDELIM2_MAXIMUM + 1; + if (size == newsizemax) + goto unlock_done; + newsize = newsizemax; + } + + nbytes_avail = newsize - (read_pos - ptr); + newptr = realloc (ptr, newsize); + if (!newptr) + goto unlock_done; + ptr = newptr; + size = newsize; + read_pos = size - nbytes_avail + ptr; + } + + /* Here, if size < nmax, nbytes_avail >= buffer_len + 1. + If size == nmax, nbytes_avail > 0. */ + + if (1 < nbytes_avail) + { + size_t copy_len = nbytes_avail - 1; + if (buffer_len < copy_len) + copy_len = buffer_len; + if (buffer) + memcpy (read_pos, buffer, copy_len); + else + *read_pos = c; + read_pos += copy_len; + nbytes_avail -= copy_len; + } + + /* Here still nbytes_avail > 0. */ + + if (buffer && freadseek (stream, buffer_len)) + goto unlock_done; + } + while (!found_delimiter); + + /* Done - NUL terminate and return the number of bytes read. + At this point we know that nbytes_avail >= 1. */ + *read_pos = '\0'; + + bytes_stored = read_pos - (ptr + offset); + + unlock_done: + funlockfile (stream); + + done: + *lineptr = ptr; + *linesize = size; + return bytes_stored ? bytes_stored : -1; +} |