summaryrefslogtreecommitdiff
path: root/polux/application/busybox/libbb/read.c
diff options
context:
space:
mode:
Diffstat (limited to 'polux/application/busybox/libbb/read.c')
-rw-r--r--polux/application/busybox/libbb/read.c227
1 files changed, 227 insertions, 0 deletions
diff --git a/polux/application/busybox/libbb/read.c b/polux/application/busybox/libbb/read.c
new file mode 100644
index 0000000000..5754465360
--- /dev/null
+++ b/polux/application/busybox/libbb/read.c
@@ -0,0 +1,227 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Utility routines.
+ *
+ * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#include "libbb.h"
+
+ssize_t safe_read(int fd, void *buf, size_t count)
+{
+ ssize_t n;
+
+ do {
+ n = read(fd, buf, count);
+ } while (n < 0 && errno == EINTR);
+
+ return n;
+}
+
+/* Suppose that you are a shell. You start child processes.
+ * They work and eventually exit. You want to get user input.
+ * You read stdin. But what happens if last child switched
+ * its stdin into O_NONBLOCK mode?
+ *
+ * *** SURPRISE! It will affect the parent too! ***
+ * *** BIG SURPRISE! It stays even after child exits! ***
+ *
+ * This is a design bug in UNIX API.
+ * fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0) | O_NONBLOCK);
+ * will set nonblocking mode not only on _your_ stdin, but
+ * also on stdin of your parent, etc.
+ *
+ * In general,
+ * fd2 = dup(fd1);
+ * fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL, 0) | O_NONBLOCK);
+ * sets both fd1 and fd2 to O_NONBLOCK. This includes cases
+ * where duping is done implicitly by fork() etc.
+ *
+ * We need
+ * fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD, 0) | O_NONBLOCK);
+ * (note SETFD, not SETFL!) but such thing doesn't exist.
+ *
+ * Alternatively, we need nonblocking_read(fd, ...) which doesn't
+ * require O_NONBLOCK dance at all. Actually, it exists:
+ * n = recv(fd, buf, len, MSG_DONTWAIT);
+ * "MSG_DONTWAIT:
+ * Enables non-blocking operation; if the operation
+ * would block, EAGAIN is returned."
+ * but recv() works only for sockets!
+ *
+ * So far I don't see any good solution, I can only propose
+ * that affected readers should be careful and use this routine,
+ * which detects EAGAIN and uses poll() to wait on the fd.
+ * Thankfully, poll() doesn't care about O_NONBLOCK flag.
+ */
+ssize_t nonblock_safe_read(int fd, void *buf, size_t count)
+{
+ struct pollfd pfd[1];
+ ssize_t n;
+
+ while (1) {
+ n = safe_read(fd, buf, count);
+ if (n >= 0 || errno != EAGAIN)
+ return n;
+ /* fd is in O_NONBLOCK mode. Wait using poll and repeat */
+ pfd[0].fd = fd;
+ pfd[0].events = POLLIN;
+ safe_poll(pfd, 1, -1);
+ }
+}
+
+/*
+ * Read all of the supplied buffer from a file.
+ * This does multiple reads as necessary.
+ * Returns the amount read, or -1 on an error.
+ * A short read is returned on an end of file.
+ */
+ssize_t full_read(int fd, void *buf, size_t len)
+{
+ ssize_t cc;
+ ssize_t total;
+
+ total = 0;
+
+ while (len) {
+ cc = safe_read(fd, buf, len);
+
+ if (cc < 0) {
+ if (total) {
+ /* we already have some! */
+ /* user can do another read to know the error code */
+ return total;
+ }
+ return cc; /* read() returns -1 on failure. */
+ }
+ if (cc == 0)
+ break;
+ buf = ((char *)buf) + cc;
+ total += cc;
+ len -= cc;
+ }
+
+ return total;
+}
+
+// Die with an error message if we can't read the entire buffer.
+void xread(int fd, void *buf, size_t count)
+{
+ if (count) {
+ ssize_t size = full_read(fd, buf, count);
+ if (size != count)
+ bb_error_msg_and_die("short read");
+ }
+}
+
+// Die with an error message if we can't read one character.
+unsigned char xread_char(int fd)
+{
+ char tmp;
+ xread(fd, &tmp, 1);
+ return tmp;
+}
+
+// Read one line a-la fgets. Works only on seekable streams
+char *reads(int fd, char *buffer, size_t size)
+{
+ char *p;
+
+ if (size < 2)
+ return NULL;
+ size = full_read(fd, buffer, size-1);
+ if ((ssize_t)size <= 0)
+ return NULL;
+
+ buffer[size] = '\0';
+ p = strchr(buffer, '\n');
+ if (p) {
+ off_t offset;
+ *p++ = '\0';
+ // avoid incorrect (unsigned) widening
+ offset = (off_t)(p-buffer) - (off_t)size;
+ // set fd position right after '\n'
+ if (offset && lseek(fd, offset, SEEK_CUR) == (off_t)-1)
+ return NULL;
+ }
+ return buffer;
+}
+
+// Read one line a-la fgets. Reads byte-by-byte.
+// Useful when it is important to not read ahead.
+// Bytes are appended to pfx (which must be malloced, or NULL).
+char *xmalloc_reads(int fd, char *buf)
+{
+ char *p;
+ int sz = buf ? strlen(buf) : 0;
+
+ goto jump_in;
+ while (1) {
+ if (p - buf == sz) {
+ jump_in:
+ buf = xrealloc(buf, sz + 128);
+ p = buf + sz;
+ sz += 128;
+ }
+ /* nonblock_safe_read() because we are used by e.g. shells */
+ if (nonblock_safe_read(fd, p, 1) != 1) { /* EOF/error */
+ if (p == buf) { /* we read nothing */
+ free(buf);
+ return NULL;
+ }
+ break;
+ }
+ if (*p == '\n')
+ break;
+ p++;
+ }
+ *p++ = '\0';
+ return xrealloc(buf, p - buf);
+}
+
+ssize_t read_close(int fd, void *buf, size_t size)
+{
+ /*int e;*/
+ size = full_read(fd, buf, size);
+ /*e = errno;*/
+ close(fd);
+ /*errno = e;*/
+ return size;
+}
+
+ssize_t open_read_close(const char *filename, void *buf, size_t size)
+{
+ int fd = open(filename, O_RDONLY);
+ if (fd < 0)
+ return fd;
+ return read_close(fd, buf, size);
+}
+
+// Read (potentially big) files in one go. File size is estimated by
+// lseek to end.
+void *xmalloc_open_read_close(const char *filename, size_t *sizep)
+{
+ char *buf;
+ size_t size = sizep ? *sizep : INT_MAX;
+ int fd;
+ off_t len;
+
+ fd = xopen(filename, O_RDONLY);
+ /* /proc/N/stat files report len 0 here */
+ /* In order to make such files readable, we add small const */
+ len = xlseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */
+ xlseek(fd, 0, SEEK_SET);
+ if (len < size)
+ size = len;
+ buf = xmalloc(size + 1);
+ size = read_close(fd, buf, size);
+ if ((ssize_t)size < 0)
+ bb_perror_msg_and_die("'%s'", filename);
+ xrealloc(buf, size + 1);
+ buf[size] = '\0';
+ if (sizep)
+ *sizep = size;
+ return buf;
+}