mirror of
https://github.com/sheumann/hush.git
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373 lines
9.0 KiB
C
373 lines
9.0 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Utility routines.
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*
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* Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
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*
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* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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*/
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#include "libbb.h"
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#define ZIPPED (ENABLE_FEATURE_SEAMLESS_LZMA \
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|| ENABLE_FEATURE_SEAMLESS_BZ2 \
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|| ENABLE_FEATURE_SEAMLESS_GZ \
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/* || ENABLE_FEATURE_SEAMLESS_Z */ \
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)
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#if ZIPPED
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# include "archive.h"
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#endif
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/* Suppose that you are a shell. You start child processes.
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* They work and eventually exit. You want to get user input.
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* You read stdin. But what happens if last child switched
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* its stdin into O_NONBLOCK mode?
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*
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* *** SURPRISE! It will affect the parent too! ***
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* *** BIG SURPRISE! It stays even after child exits! ***
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*
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* This is a design bug in UNIX API.
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* fcntl(0, F_SETFL, fcntl(0, F_GETFL) | O_NONBLOCK);
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* will set nonblocking mode not only on _your_ stdin, but
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* also on stdin of your parent, etc.
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*
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* In general,
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* fd2 = dup(fd1);
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* fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL) | O_NONBLOCK);
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* sets both fd1 and fd2 to O_NONBLOCK. This includes cases
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* where duping is done implicitly by fork() etc.
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*
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* We need
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* fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD) | O_NONBLOCK);
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* (note SETFD, not SETFL!) but such thing doesn't exist.
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*
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* Alternatively, we need nonblocking_read(fd, ...) which doesn't
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* require O_NONBLOCK dance at all. Actually, it exists:
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* n = recv(fd, buf, len, MSG_DONTWAIT);
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* "MSG_DONTWAIT:
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* Enables non-blocking operation; if the operation
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* would block, EAGAIN is returned."
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* but recv() works only for sockets!
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*
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* So far I don't see any good solution, I can only propose
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* that affected readers should be careful and use this routine,
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* which detects EAGAIN and uses poll() to wait on the fd.
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* Thankfully, poll() doesn't care about O_NONBLOCK flag.
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*/
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ssize_t FAST_FUNC nonblock_safe_read(int fd, void *buf, size_t count)
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{
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struct pollfd pfd[1];
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ssize_t n;
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while (1) {
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n = safe_read(fd, buf, count);
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if (n >= 0 || errno != EAGAIN)
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return n;
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/* fd is in O_NONBLOCK mode. Wait using poll and repeat */
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pfd[0].fd = fd;
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pfd[0].events = POLLIN;
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safe_poll(pfd, 1, -1); /* note: this pulls in printf */
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}
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}
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// Reads one line a-la fgets (but doesn't save terminating '\n').
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// Reads byte-by-byte. Useful when it is important to not read ahead.
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// Bytes are appended to pfx (which must be malloced, or NULL).
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char* FAST_FUNC xmalloc_reads(int fd, char *buf, size_t *maxsz_p)
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{
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char *p;
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size_t sz = buf ? strlen(buf) : 0;
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size_t maxsz = maxsz_p ? *maxsz_p : (INT_MAX - 4095);
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goto jump_in;
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while (sz < maxsz) {
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if ((size_t)(p - buf) == sz) {
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jump_in:
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buf = xrealloc(buf, sz + 128);
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p = buf + sz;
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sz += 128;
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}
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/* nonblock_safe_read() because we are used by e.g. shells */
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if (nonblock_safe_read(fd, p, 1) != 1) { /* EOF/error */
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if (p == buf) { /* we read nothing */
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free(buf);
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return NULL;
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}
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break;
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}
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if (*p == '\n')
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break;
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p++;
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}
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*p = '\0';
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if (maxsz_p)
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*maxsz_p = p - buf;
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p++;
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return xrealloc(buf, p - buf);
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}
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// Read (potentially big) files in one go. File size is estimated
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// by stat. Extra '\0' byte is appended.
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void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
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{
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char *buf;
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size_t size, rd_size, total;
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size_t to_read;
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struct stat st;
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to_read = maxsz_p ? *maxsz_p : (INT_MAX - 4095); /* max to read */
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/* Estimate file size */
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st.st_size = 0; /* in case fstat fails, assume 0 */
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fstat(fd, &st);
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/* /proc/N/stat files report st_size 0 */
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/* In order to make such files readable, we add small const */
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size = (st.st_size | 0x3ff) + 1;
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total = 0;
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buf = NULL;
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while (1) {
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if (to_read < size)
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size = to_read;
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buf = xrealloc(buf, total + size + 1);
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rd_size = full_read(fd, buf + total, size);
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if ((ssize_t)rd_size == (ssize_t)(-1)) { /* error */
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free(buf);
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return NULL;
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}
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total += rd_size;
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if (rd_size < size) /* EOF */
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break;
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if (to_read <= rd_size)
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break;
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to_read -= rd_size;
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/* grow by 1/8, but in [1k..64k] bounds */
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size = ((total / 8) | 0x3ff) + 1;
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if (size > 64*1024)
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size = 64*1024;
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}
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buf = xrealloc(buf, total + 1);
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buf[total] = '\0';
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if (maxsz_p)
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*maxsz_p = total;
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return buf;
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}
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#ifdef USING_LSEEK_TO_GET_SIZE
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/* Alternatively, file size can be obtained by lseek to the end.
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* The code is slightly bigger. Retained in case fstat approach
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* will not work for some weird cases (/proc, block devices, etc).
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* (NB: lseek also can fail to work for some weird files) */
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// Read (potentially big) files in one go. File size is estimated by
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// lseek to end.
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void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
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{
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char *buf;
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size_t size;
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int fd;
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off_t len;
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fd = open(filename, O_RDONLY);
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if (fd < 0)
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return NULL;
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/* /proc/N/stat files report len 0 here */
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/* In order to make such files readable, we add small const */
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size = 0x3ff; /* read only 1k on unseekable files */
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len = lseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */
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if (len != (off_t)-1) {
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xlseek(fd, 0, SEEK_SET);
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size = maxsz_p ? *maxsz_p : (INT_MAX - 4095);
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if (len < size)
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size = len;
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}
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buf = xmalloc(size + 1);
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size = read_close(fd, buf, size);
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if ((ssize_t)size < 0) {
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free(buf);
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return NULL;
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}
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buf = xrealloc(buf, size + 1);
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buf[size] = '\0';
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if (maxsz_p)
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*maxsz_p = size;
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return buf;
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}
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#endif
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// Read (potentially big) files in one go. File size is estimated
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// by stat.
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void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
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{
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char *buf;
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int fd;
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fd = open(filename, O_RDONLY);
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if (fd < 0)
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return NULL;
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buf = xmalloc_read(fd, maxsz_p);
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close(fd);
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return buf;
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}
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/* Die with an error message if we can't read the entire buffer. */
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void FAST_FUNC xread(int fd, void *buf, size_t count)
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{
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if (count) {
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ssize_t size = full_read(fd, buf, count);
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if ((size_t)size != count)
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bb_error_msg_and_die("short read");
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}
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}
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/* Die with an error message if we can't read one character. */
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unsigned char FAST_FUNC xread_char(int fd)
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{
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char tmp;
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xread(fd, &tmp, 1);
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return tmp;
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}
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void* FAST_FUNC xmalloc_xopen_read_close(const char *filename, size_t *maxsz_p)
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{
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void *buf = xmalloc_open_read_close(filename, maxsz_p);
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if (!buf)
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bb_perror_msg_and_die("can't read '%s'", filename);
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return buf;
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}
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/* Used by e.g. rpm which gives us a fd without filename,
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* thus we can't guess the format from filename's extension.
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*/
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#if ZIPPED
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void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
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{
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const int fail_if_not_detected = 1;
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union {
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uint8_t b[4];
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uint16_t b16[2];
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uint32_t b32[1];
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} magic;
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int offset = -2;
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# if BB_MMU
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IF_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
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enum { xformer_prog = 0 };
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# else
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enum { xformer = 0 };
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const char *xformer_prog;
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# endif
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/* .gz and .bz2 both have 2-byte signature, and their
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* unpack_XXX_stream wants this header skipped. */
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xread(fd, magic.b16, sizeof(magic.b16[0]));
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if (ENABLE_FEATURE_SEAMLESS_GZ
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&& magic.b16[0] == GZIP_MAGIC
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) {
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# if BB_MMU
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xformer = unpack_gz_stream;
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# else
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xformer_prog = "gunzip";
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# endif
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goto found_magic;
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}
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if (ENABLE_FEATURE_SEAMLESS_BZ2
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&& magic.b16[0] == BZIP2_MAGIC
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) {
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# if BB_MMU
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xformer = unpack_bz2_stream;
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# else
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xformer_prog = "bunzip2";
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# endif
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goto found_magic;
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}
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if (ENABLE_FEATURE_SEAMLESS_XZ
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&& magic.b16[0] == XZ_MAGIC1
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) {
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offset = -6;
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xread(fd, magic.b32, sizeof(magic.b32[0]));
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if (magic.b32[0] == XZ_MAGIC2) {
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# if BB_MMU
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xformer = unpack_xz_stream;
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/* unpack_xz_stream wants fd at position 6, no need to seek */
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//xlseek(fd, offset, SEEK_CUR);
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# else
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xformer_prog = "unxz";
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# endif
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goto found_magic;
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}
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}
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/* No known magic seen */
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if (fail_if_not_detected)
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bb_error_msg_and_die("no gzip"
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IF_FEATURE_SEAMLESS_BZ2("/bzip2")
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IF_FEATURE_SEAMLESS_XZ("/xz")
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" magic");
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xlseek(fd, offset, SEEK_CUR);
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return;
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found_magic:
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# if !BB_MMU
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/* NOMMU version of open_transformer execs
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* an external unzipper that wants
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* file position at the start of the file */
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xlseek(fd, offset, SEEK_CUR);
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# endif
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open_transformer(fd, xformer, xformer_prog);
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}
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#endif /* ZIPPED */
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int FAST_FUNC open_zipped(const char *fname)
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{
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#if !ZIPPED
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return open(fname, O_RDONLY);
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#else
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char *sfx;
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int fd;
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fd = open(fname, O_RDONLY);
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if (fd < 0)
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return fd;
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sfx = strrchr(fname, '.');
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if (sfx) {
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sfx++;
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if (ENABLE_FEATURE_SEAMLESS_LZMA && strcmp(sfx, "lzma") == 0)
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/* .lzma has no header/signature, just trust it */
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open_transformer(fd, unpack_lzma_stream, "unlzma");
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else
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if ((ENABLE_FEATURE_SEAMLESS_GZ && strcmp(sfx, "gz") == 0)
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|| (ENABLE_FEATURE_SEAMLESS_BZ2 && strcmp(sfx, "bz2") == 0)
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|| (ENABLE_FEATURE_SEAMLESS_XZ && strcmp(sfx, "xz") == 0)
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) {
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setup_unzip_on_fd(fd /*, fail_if_not_detected: 1*/);
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}
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}
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return fd;
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#endif
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}
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void* FAST_FUNC xmalloc_open_zipped_read_close(const char *fname, size_t *maxsz_p)
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{
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int fd;
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char *image;
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fd = open_zipped(fname);
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if (fd < 0)
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return NULL;
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image = xmalloc_read(fd, maxsz_p);
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if (!image)
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bb_perror_msg("read error from '%s'", fname);
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close(fd);
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return image;
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}
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