1 files changed, 86 insertions, 0 deletions
diff --git a/usr/kinit/readfile.c b/usr/kinit/readfile.c
new file mode 100644
index 0000000..7a16b4a
--- /dev/null
+++ b/usr/kinit/readfile.c
@@ -0,0 +1,86 @@
+/*
+ * Read the entire contents of a file into malloc'd storage.  This
+ * is mostly useful for things like /proc files where we can't just
+ * fstat() to get the length and then mmap().
+ *
+ * Returns the number of bytes read, or -1 on error.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <sys/stat.h>
+
+#include "kinit.h"
+
+ssize_t freadfile(FILE *f, char **pp)
+{
+	size_t bs;		/* Decent starting point... */
+	size_t bf;		/* Bytes free */
+	size_t bu = 0;		/* Bytes used */
+	char *buffer, *nb;
+	size_t rv;
+	int old_errno = errno;
+
+	bs = BUFSIZ;		/* A guess as good as any */
+	bf = bs;
+	buffer = malloc(bs);
+
+	if (!buffer)
+		return -1;
+
+	for (;;) {
+		errno = 0;
+
+		while (bf && (rv = _fread(buffer + bu, bf, f))) {
+			bu += rv;
+			bf -= rv;
+		}
+
+		if (errno && errno != EINTR && errno != EAGAIN) {
+			/* error */
+			free(buffer);
+			return -1;
+		}
+
+		if (bf) {
+			/* Hit EOF, no error */
+
+			/* Try to free superfluous memory */
+			if ((nb = realloc(buffer, bu + 1)))
+				buffer = nb;
+
+			/* Null-terminate result for good measure */
+			buffer[bu] = '\0';
+
+			*pp = buffer;
+			errno = old_errno;
+			return bu;
+		}
+
+		/* Double the size of the buffer */
+		bf += bs;
+		bs += bs;
+		if (!(nb = realloc(buffer, bs))) {
+			/* out of memory error */
+			free(buffer);
+			return -1;
+		}
+		buffer = nb;
+	}
+}
+
+ssize_t readfile(const char *filename, char **pp)
+{
+	FILE *f = fopen(filename, "r");
+	ssize_t rv;
+
+	if (!f)
+		return -1;
+
+	rv = freadfile(f, pp);
+
+	fclose(f);
+
+	return rv;
+}