/* fmemopen implementation. Copyright (C) 2015-2017 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library 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. The GNU C Library 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 the GNU C Library; if not, see <http://www.gnu.org/licenses/>. */ /* fmemopen() from 2.22 and forward works as defined by POSIX. It also provides an older symbol, version 2.2.5, that behaves different regarding SEEK_END (libio/oldfmemopen.c). */ #include <errno.h> #include <libio.h> #include <stdio.h> #include <stdlib.h> #include <stdint.h> #include <string.h> #include <sys/types.h> #include "libioP.h" typedef struct fmemopen_cookie_struct fmemopen_cookie_t; struct fmemopen_cookie_struct { char *buffer; /* memory buffer. */ int mybuffer; /* allocated my buffer? */ int append; /* buffer open for append? */ size_t size; /* buffer length in bytes. */ _IO_off64_t pos; /* current position at the buffer. */ size_t maxpos; /* max position in buffer. */ }; static ssize_t fmemopen_read (void *cookie, char *b, size_t s) { fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie; if (c->pos + s > c->maxpos) { s = c->maxpos - c->pos; if ((size_t) c->pos > c->maxpos) s = 0; } memcpy (b, &(c->buffer[c->pos]), s); c->pos += s; return s; } static ssize_t fmemopen_write (void *cookie, const char *b, size_t s) { fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;; _IO_off64_t pos = c->append ? c->maxpos : c->pos; int addnullc = (s == 0 || b[s - 1] != '\0'); if (pos + s > c->size) { if ((size_t) (c->pos + addnullc) >= c->size) { __set_errno (ENOSPC); return 0; } s = c->size - pos; } memcpy (&(c->buffer[pos]), b, s); c->pos = pos + s; if ((size_t) c->pos > c->maxpos) { c->maxpos = c->pos; if (c->maxpos < c->size && addnullc) c->buffer[c->maxpos] = '\0'; /* A null byte is written in a stream open for update iff it fits. */ else if (c->append == 0 && addnullc != 0) c->buffer[c->size-1] = '\0'; } return s; } static int fmemopen_seek (void *cookie, _IO_off64_t *p, int w) { _IO_off64_t np; fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie; switch (w) { case SEEK_SET: np = *p; break; case SEEK_CUR: np = c->pos + *p; break; case SEEK_END: np = c->maxpos + *p; break; default: return -1; } if (np < 0 || (size_t) np > c->size) { __set_errno (EINVAL); return -1; } *p = c->pos = np; return 0; } static int fmemopen_close (void *cookie) { fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie; if (c->mybuffer) free (c->buffer); free (c); return 0; } FILE * __fmemopen (void *buf, size_t len, const char *mode) { cookie_io_functions_t iof; fmemopen_cookie_t *c; FILE *result; c = (fmemopen_cookie_t *) calloc (sizeof (fmemopen_cookie_t), 1); if (c == NULL) return NULL; c->mybuffer = (buf == NULL); if (c->mybuffer) { c->buffer = (char *) malloc (len); if (c->buffer == NULL) { free (c); return NULL; } c->buffer[0] = '\0'; } else { if (__glibc_unlikely ((uintptr_t) len > -(uintptr_t) buf)) { free (c); __set_errno (EINVAL); return NULL; } c->buffer = buf; /* POSIX states that w+ mode should truncate the buffer. */ if (mode[0] == 'w' && mode[1] == '+') c->buffer[0] = '\0'; if (mode[0] == 'a') c->maxpos = strnlen (c->buffer, len); } /* Mode | starting position (cookie::pos) | size (cookie::size) ------ |----------------------------------|----------------------------- read | beginning of the buffer | size argument write | beginning of the buffer | zero append | first null or size buffer + 1 | first null or size argument */ c->size = len; if (mode[0] == 'r') c->maxpos = len; c->append = mode[0] == 'a'; if (c->append) c->pos = c->maxpos; else c->pos = 0; iof.read = fmemopen_read; iof.write = fmemopen_write; iof.seek = fmemopen_seek; iof.close = fmemopen_close; result = _IO_fopencookie (c, mode, iof); if (__glibc_unlikely (result == NULL)) { if (c->mybuffer) free (c->buffer); free (c); } return result; } libc_hidden_def (__fmemopen) versioned_symbol (libc, __fmemopen, fmemopen, GLIBC_2_22);