Add utils-file and provide json-c

This is an intermediate commit providing
new features for common utils.

Change-Id: Ide92167d8e4e5013ddadd718c02071ea837938e3
Signed-off-by: José Bollo <jose.bollo@iot.bzh>

1 files changed, 129 insertions, 0 deletions

diff --git a/src/utils-file.c b/src/utils-file.c
new file mode 100644
index 0000000..09eaaed
--- /dev/null
+++ b/src/utils-file.c
@@ -0,0 +1,129 @@
+/*
+ Copyright 2017 IoT.bzh
+
+ author: José Bollo <jose.bollo@iot.bzh>
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "utils-file.h"
+
+/* alias for getfile_at(AT_FDCWD, file, content, size) */
+int getfile(const char *file, char **content, size_t *size)
+{
+	return getfile_at(AT_FDCWD, file, content, size);
+}
+
+/*
+ * Reads the 'file' relative to 'dfd' (see openat) in a freshly
+ * allocated memory and returns it in 'content' and 'size' (if not NULL).
+ * To help in reading text files, a pending null is added at the
+ * end of the content.
+ * Return 0 in case of success or else -1 and set 'errno'.
+ */
+int getfile_at(int dfd, const char *file, char **content, size_t *size)
+{
+	int rc, f;
+	struct stat s;
+	char *r;
+	ssize_t rsz;
+	size_t sz, i;
+
+	if (content)
+		*content = NULL;
+	rc = openat(dfd, file, O_RDONLY);
+	if (rc >= 0) {
+		f = rc;
+		rc = fstat(f, &s);
+		if (rc != 0) {
+			/* nothing */;
+		} else if (!S_ISREG(s.st_mode)) {
+			rc = -1;
+			errno = EBADF;
+		} else {
+			sz = (size_t)s.st_size;
+			if (content) {
+				r = malloc(sz + 1);
+				if (!r) {
+					errno = ENOMEM;
+					rc = -1;
+				} else {
+					i = 0;
+					while (!rc && i < sz) {
+						rsz = read(f, r + i, sz - i);
+						if (rsz == 0)
+							sz = i;
+						else if (rsz > 0)
+							i += (size_t)rsz;
+						else if (errno != EINTR && errno != EAGAIN) {
+							free(r);
+							rc = -1;
+						}
+					}
+					if (rc == 0) {
+						r[sz] = 0;
+						*content = r;
+					}
+				}
+			}
+			if (size)
+				*size = sz;
+		}
+		close(f);
+	}
+	return rc;
+}
+
+/* alias for putfile_at(AT_FDCWD, file, content, size) */
+int putfile(const char *file, const void *content, size_t size)
+{
+	return putfile_at(AT_FDCWD, file, content, size);
+}
+
+int putfile_at(int dfd, const char *file, const void *content, size_t size)
+{
+	int rc, f;
+	ssize_t wsz;
+	size_t i;
+
+	rc = openat(dfd, file, O_WRONLY|O_CREAT|O_TRUNC, 0666);
+	if (rc >= 0) {
+		if (size == (size_t)(ssize_t)-1)
+			size = strlen(content);
+		f = rc;
+		if (rc < 0)
+		i = 0;
+		rc = 0;
+		while (!rc && i < size) {
+			wsz = write(f, content + i, size - i);
+			if (wsz >= 0)
+				i += (size_t)wsz;
+			else if (errno != EINTR && errno != EAGAIN) {
+				unlinkat(dfd, file, 0);
+				rc = -1;
+			}
+		}
+		close(f);
+	}
+	return rc;
+}
+