diff options
Diffstat (limited to 'libio/fmemopen.c')
| -rw-r--r-- | libio/fmemopen.c | 140 |
1 files changed, 47 insertions, 93 deletions
diff --git a/libio/fmemopen.c b/libio/fmemopen.c index 06e5ab8..e6e6a49 100644 --- a/libio/fmemopen.c +++ b/libio/fmemopen.c @@ -1,7 +1,6 @@ -/* Fmemopen implementation. - Copyright (C) 2000-2015 Free Software Foundation, Inc. +/* fmemopen implementation. + Copyright (C) 2015 Free Software Foundation, Inc. This file is part of the GNU C Library. - Contributed by Hanno Mueller, kontakt@hanno.de, 2000. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public @@ -17,54 +16,10 @@ License along with the GNU C Library; if not, see <http://www.gnu.org/licenses/>. */ -/* - * fmemopen() - "my" version of a string stream - * Hanno Mueller, kontakt@hanno.de - * - * - * I needed fmemopen() for an application that I currently work on, - * but couldn't find it in libio. The following snippet of code is an - * attempt to implement what glibc's documentation describes. - * - * - * - * I already see some potential problems: - * - * - I never used the "original" fmemopen(). I am sure that "my" - * fmemopen() behaves differently than the original version. - * - * - The documentation doesn't say wether a string stream allows - * seeks. I checked the old fmemopen implementation in glibc's stdio - * directory, wasn't quite able to see what is going on in that - * source, but as far as I understand there was no seek there. For - * my application, I needed fseek() and ftell(), so it's here. - * - * - "append" mode and fseek(p, SEEK_END) have two different ideas - * about the "end" of the stream. - * - * As described in the documentation, when opening the file in - * "append" mode, the position pointer will be set to the first null - * character of the string buffer (yet the buffer may already - * contain more data). For fseek(), the last byte of the buffer is - * used as the end of the stream. - * - * - It is unclear to me what the documentation tries to say when it - * explains what happens when you use fmemopen with a NULL - * buffer. - * - * Quote: "fmemopen [then] allocates an array SIZE bytes long. This - * is really only useful if you are going to write things to the - * buffer and then read them back in again." - * - * What does that mean if the original fmemopen() did not allow - * seeking? How do you read what you just wrote without seeking back - * to the beginning of the stream? - * - * - I think there should be a second version of fmemopen() that does - * not add null characters for each write. (At least in my - * application, I am not actually using strings but binary data and - * so I don't need the stream to add null characters on its own.) - */ +/* 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> @@ -79,25 +34,23 @@ typedef struct fmemopen_cookie_struct fmemopen_cookie_t; struct fmemopen_cookie_struct { - char *buffer; - int mybuffer; - int binmode; - size_t size; - _IO_off64_t pos; - size_t maxpos; + 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; - - c = (fmemopen_cookie_t *) cookie; + fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie; - if (c->pos + s > c->size) + if (c->pos + s > c->maxpos) { - if ((size_t) c->pos == c->size) + if ((size_t) c->pos == c->maxpos) return 0; s = c->size - c->pos; } @@ -115,29 +68,28 @@ fmemopen_read (void *cookie, char *b, size_t s) static ssize_t fmemopen_write (void *cookie, const char *b, size_t s) { - fmemopen_cookie_t *c; + fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;; + _IO_off64_t pos = c->append ? c->maxpos : c->pos; int addnullc; - c = (fmemopen_cookie_t *) cookie; - - addnullc = c->binmode == 0 && (s == 0 || b[s - 1] != '\0'); + addnullc = (s == 0 || b[s - 1] != '\0'); - if (c->pos + s + addnullc > c->size) + if (pos + s + addnullc > c->size) { if ((size_t) (c->pos + addnullc) >= c->size) { __set_errno (ENOSPC); return 0; } - s = c->size - c->pos - addnullc; + s = c->size - pos - addnullc; } - memcpy (&(c->buffer[c->pos]), b, s); + memcpy (&(c->buffer[pos]), b, s); - c->pos += s; - if ((size_t) c->pos > c->maxpos) + pos += s; + if ((size_t) pos > c->maxpos) { - c->maxpos = c->pos; + c->maxpos = pos; if (addnullc) c->buffer[c->maxpos] = '\0'; } @@ -150,9 +102,7 @@ static int fmemopen_seek (void *cookie, _IO_off64_t *p, int w) { _IO_off64_t np; - fmemopen_cookie_t *c; - - c = (fmemopen_cookie_t *) cookie; + fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie; switch (w) { @@ -165,7 +115,7 @@ fmemopen_seek (void *cookie, _IO_off64_t *p, int w) break; case SEEK_END: - np = (c->binmode ? c->size : c->maxpos) - *p; + np = c->maxpos + *p; break; default: @@ -184,9 +134,7 @@ fmemopen_seek (void *cookie, _IO_off64_t *p, int w) static int fmemopen_close (void *cookie) { - fmemopen_cookie_t *c; - - c = (fmemopen_cookie_t *) cookie; + fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie; if (c->mybuffer) free (c->buffer); @@ -197,18 +145,11 @@ fmemopen_close (void *cookie) FILE * -fmemopen (void *buf, size_t len, const char *mode) +__fmemopen (void *buf, size_t len, const char *mode) { cookie_io_functions_t iof; fmemopen_cookie_t *c; - if (__glibc_unlikely (len == 0)) - { - einval: - __set_errno (EINVAL); - return NULL; - } - c = (fmemopen_cookie_t *) malloc (sizeof (fmemopen_cookie_t)); if (c == NULL) return NULL; @@ -231,26 +172,38 @@ fmemopen (void *buf, size_t len, const char *mode) if (__glibc_unlikely ((uintptr_t) len > -(uintptr_t) buf)) { free (c); - goto einval; + __set_errno (EINVAL); + return NULL; } c->buffer = buf; - if (mode[0] == 'w') + /* POSIX states that w+ mode should truncate the buffer. */ + if (mode[0] == 'w' && mode[1] == '+') c->buffer[0] = '\0'; 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] == 'a') + if (mode[0] == 'r') + c->maxpos = len; + + c->append = mode[0] == 'a'; + if (c->append) c->pos = c->maxpos; else c->pos = 0; - c->binmode = mode[0] != '\0' && mode[1] == 'b'; - iof.read = fmemopen_read; iof.write = fmemopen_write; iof.seek = fmemopen_seek; @@ -258,4 +211,5 @@ fmemopen (void *buf, size_t len, const char *mode) return _IO_fopencookie (c, mode, iof); } -libc_hidden_def (fmemopen) +libc_hidden_def (__fmemopen) +versioned_symbol (libc, __fmemopen, fmemopen, GLIBC_2_22); |