perf tools: Add filename__read_str util function

Adding filename__read_str util function to read
text file and return it in the char array.

The interface is:
  int filename__read_str(const char *filename, char **buf, size_t *sizep)

  Returns 0/-1 if the read suceeded/fail respectively.

  buf  - place to store the data pointer
  size - place to store data size

v2 change:
  - better error handling suggested by Namhyung Kim.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1386076182-14484-9-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 50 insertions, 0 deletions

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index b1d5376b9dd9..bae8756a4eb1 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -6,6 +6,8 @@
 #endif
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <errno.h>
 #include <linux/kernel.h>
 
 /*
@@ -433,3 +435,50 @@ int filename__read_int(const char *filename, int *value)
         close(fd);
         return err;
 }
+
+int filename__read_str(const char *filename, char **buf, size_t *sizep)
+{
+        size_t size = 0, alloc_size = 0;
+        void *bf = NULL, *nbf;
+        int fd, n, err = 0;
+
+        fd = open(filename, O_RDONLY);
+        if (fd < 0)
+                return -errno;
+
+        do {
+                if (size == alloc_size) {
+                        alloc_size += BUFSIZ;
+                        nbf = realloc(bf, alloc_size);
+                        if (!nbf) {
+                                err = -ENOMEM;
+                                break;
+                        }
+
+                        bf = nbf;
+                }
+
+                n = read(fd, bf + size, alloc_size - size);
+                if (n < 0) {
+                        if (size) {
+                                pr_warning("read failed %d: %s\n",
+                                           errno, strerror(errno));
+                                err = 0;
+                        } else
+                                err = -errno;
+
+                        break;
+                }
+
+                size += n;
+        } while (n > 0);
+
+        if (!err) {
+                *sizep = size;
+                *buf   = bf;
+        } else
+                free(bf);
+
+        close(fd);
+        return err;
+}
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index ce0f73d4d91f..adb39f251f90 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -308,4 +308,5 @@ char *get_srcline(struct dso *dso, unsigned long addr);
 void free_srcline(char *srcline);
 
 int filename__read_int(const char *filename, int *value);
+int filename__read_str(const char *filename, char **buf, size_t *sizep);
 #endif /* GIT_COMPAT_UTIL_H */