add open_read_close() and similar stuff

git-svn-id: svn://busybox.net/trunk/busybox@16377 69ca8d6d-28ef-0310-b511-8ec308f3f277

1 files changed, 133 insertions, 0 deletions

diff --git a/libbb/read.c b/libbb/read.c
new file mode 100644
index 000000000..1c2945f45
--- /dev/null
+++ b/libbb/read.c
@@ -0,0 +1,133 @@
+/* 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;
+}
+
+/*
+ * 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)
+                        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';
+                offset = (p-buffer) - size;
+                // set fd position the right after the \n
+                if (offset && lseek(fd, offset, SEEK_CUR) == (off_t)-1)
+                        return NULL;
+        }
+        return buffer;
+}
+
+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);
+}
+
+void *xmalloc_open_read_close(const char *filename, size_t *sizep)
+{
+        char *buf;
+        size_t size = sizep ? *sizep : INT_MAX;
+        int fd = xopen(filename, O_RDONLY);
+        off_t len = xlseek(fd, 0, SEEK_END);
+        xlseek(fd, 0, SEEK_SET);
+
+        if (len > size)
+                bb_error_msg_and_die("file '%s' is too big", filename);
+        size = len;
+        buf = xmalloc(size+1);
+        size = read_close(fd, buf, size);
+        if ((ssize_t)size < 0)
+                bb_perror_msg_and_die("'%s'", filename);
+        buf[size] = '\0';
+        if (sizep) *sizep = size;
+        return buf;
+}