Mailing List Archive

# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1271090369 -3600
# Node ID df34011884a3bcf54b7ac4548a3a5bb9dd295845
# Parent 37e4d8e11554404b674fede858668f7bf8d1410b
libxl: New utility functions in for reading and writing files.

We introduce these functions in libxl_utils.h:

int libxl_read_file_contents(struct libxl_ctx *ctx, const char
*filename,
void **data_r, int *datalen_r);
int libxl_read_exactly(struct libxl_ctx *ctx, int fd, void *data,
ssize_t sz,
const char *filename, const char *what);
int libxl_write_exactly(struct libxl_ctx *ctx, int fd, const void
*data,
ssize_t sz, const char *filename, const char
*what);

They will be needed by the following patches. They have to be in
libxl.a rather than libxutil.a because they will be used, amongst
other places, in libxl itself.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
tools/libxl/libxl_utils.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++
tools/libxl/libxl_utils.h | 18 ++++++++
2 files changed, 121 insertions(+)

diff -r 37e4d8e11554 -r df34011884a3 tools/libxl/libxl_utils.c
--- a/tools/libxl/libxl_utils.c Mon Apr 12 17:38:42 2010 +0100
+++ b/tools/libxl/libxl_utils.c Mon Apr 12 17:39:29 2010 +0100
@@ -26,6 +26,7 @@
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
+#include <assert.h>

#include "libxl_utils.h"
#include "libxl_internal.h"
@@ -177,3 +178,105 @@ out:
return rc;
}

+int libxl_read_file_contents(struct libxl_ctx *ctx, const char *filename,
+ void **data_r, int *datalen_r) {
+ FILE *f = 0;
+ uint8_t *data = 0;
+ int datalen = 0;
+ int e;
+ struct stat stab;
+ ssize_t rs;
+
+ f = fopen(filename, "r");
+ if (!f) {
+ if (errno == ENOENT) return ENOENT;
+ XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "failed to open %s", filename);
+ goto xe;
+ }
+
+ if (fstat(fileno(f), &stab)) {
+ XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "failed to fstat %s", filename);
+ goto xe;
+ }
+
+ if (!S_ISREG(stab.st_mode)) {
+ XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "%s is not a plain file", filename);
+ errno = ENOTTY;
+ goto xe;
+ }
+
+ if (stab.st_size > INT_MAX) {
+ XL_LOG(ctx, XL_LOG_ERROR, "file %s is far too large", filename);
+ errno = EFBIG;
+ goto xe;
+ }
+
+ datalen = stab.st_size;
+
+ if (stab.st_size && data_r) {
+ data = malloc(datalen);
+ if (!data) goto xe;
+
+ rs = fread(data, 1, datalen, f);
+ if (rs != datalen) {
+ if (ferror(f))
+ XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "failed to read %s", filename);
+ else if (feof(f))
+ XL_LOG(ctx, XL_LOG_ERROR, "%s changed size while we"
+ " were reading it", filename);
+ else
+ abort();
+ goto xe;
+ }
+ }
+
+ if (fclose(f)) {
+ f = 0;
+ XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "failed to close %s", filename);
+ goto xe;
+ }
+
+ if (data_r) *data_r = data;
+ if (datalen_r) *datalen_r = datalen;
+
+ return 0;
+
+ xe:
+ e = errno;
+ assert(e != ENOENT);
+ if (f) fclose(f);
+ if (data) free(data);
+ return e;
+}
+
+#define READ_WRITE_EXACTLY(rw, zero_is_eof, constdata) \
+ \
+ int libxl_##rw##_exactly(struct libxl_ctx *ctx, int fd, \
+ constdata void *data, ssize_t sz, \
+ const char *filename, const char *what) { \
+ ssize_t got; \
+ \
+ while (sz > 0) { \
+ got = rw(fd, data, sz); \
+ if (got == -1) { \
+ if (errno == EINTR) continue; \
+ XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "failed to " #rw " %s%s%s", \
+ what?what:"", what?" from ":"", filename); \
+ return errno; \
+ } \
+ if (got == 0) { \
+ XL_LOG(ctx, XL_LOG_ERROR, \
+ zero_is_eof \
+ ? "file/stream truncated reading %s%s%s" \
+ : "file/stream write returned 0! writing %s%s%s", \
+ what?what:"", what?" from ":"", filename); \
+ return EPROTO; \
+ } \
+ sz -= got; \
+ data = (char*)data + got; \
+ } \
+ return 0; \
+ }
+
+READ_WRITE_EXACTLY(read, 1, /* */)
+READ_WRITE_EXACTLY(write, 0, const)
diff -r 37e4d8e11554 -r df34011884a3 tools/libxl/libxl_utils.h
--- a/tools/libxl/libxl_utils.h Mon Apr 12 17:38:42 2010 +0100
+++ b/tools/libxl/libxl_utils.h Mon Apr 12 17:39:29 2010 +0100
@@ -26,5 +26,23 @@ int libxl_create_logfile(struct libxl_ct
int libxl_create_logfile(struct libxl_ctx *ctx, char *name, char **full_name);
int libxl_string_to_phystype(struct libxl_ctx *ctx, char *s, libxl_disk_phystype *phystype);

+int libxl_read_file_contents(struct libxl_ctx *ctx, const char *filename,
+ void **data_r, int *datalen_r);
+ /* Reads the contents of the plain file filename into a mallocd
+ * buffer. Returns 0 or errno. Any errors other than ENOENT are logged.
+ * If the file is empty, *data_r and *datalen_r are set to 0.
+ * On error, *data_r and *datalen_r are undefined.
+ * data_r and/or datalen_r may be 0.
+ */
+
+int libxl_read_exactly(struct libxl_ctx *ctx, int fd, void *data, ssize_t sz,
+ const char *filename, const char *what);
+int libxl_write_exactly(struct libxl_ctx *ctx, int fd, const void *data,
+ ssize_t sz, const char *filename, const char *what);
+ /* Returns 0 or errno. If file is truncated on reading, returns
+ * EPROTO and you have no way to tell how much was read. Errors are
+ * logged using filename (which is only used for logging) and what
+ * (which may be 0). */
+
#endif


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