add open_read_close() and similar stuff

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;
+}