1 files changed, 45 insertions, 7 deletions
diff --git a/include/qemu/cutils.h b/include/qemu/cutils.h
index 92c927a6a3..da15547bfb 100644
--- a/include/qemu/cutils.h
+++ b/include/qemu/cutils.h
@@ -187,9 +187,39 @@ char *freq_to_str(uint64_t freq_hz);
 /* used to print char* safely */
 #define STR_OR_NULL(str) ((str) ? (str) : "null")
 
-bool buffer_is_zero(const void *buf, size_t len);
+/*
+ * Check if a buffer is all zeroes.
+ */
+
+bool buffer_is_zero_ool(const void *vbuf, size_t len);
+bool buffer_is_zero_ge256(const void *vbuf, size_t len);
 bool test_buffer_is_zero_next_accel(void);
 
+static inline bool buffer_is_zero_sample3(const char *buf, size_t len)
+{
+    /*
+     * For any reasonably sized buffer, these three samples come from
+     * three different cachelines.  In qemu-img usage, we find that
+     * each byte eliminates more than half of all buffer testing.
+     * It is therefore critical to performance that the byte tests
+     * short-circuit, so that we do not pull in additional cache lines.
+     * Do not "optimize" this to !(a | b | c).
+     */
+    return !buf[0] && !buf[len - 1] && !buf[len / 2];
+}
+
+#ifdef __OPTIMIZE__
+static inline bool buffer_is_zero(const void *buf, size_t len)
+{
+    return (__builtin_constant_p(len) && len >= 256
+            ? buffer_is_zero_sample3(buf, len) &&
+              buffer_is_zero_ge256(buf, len)
+            : buffer_is_zero_ool(buf, len));
+}
+#else
+#define buffer_is_zero  buffer_is_zero_ool
+#endif
+
 /*
  * Implementation of ULEB128 (http://en.wikipedia.org/wiki/LEB128)
  * Input is limited to 14-bit numbers
@@ -252,13 +282,21 @@ static inline const char *yes_no(bool b)
  */
 int parse_debug_env(const char *name, int max, int initial);
 
-/*
- * Hexdump a line of a byte buffer into a hexadecimal/ASCII buffer
+/**
+ * qemu_hexdump_line:
+ * @str: GString into which to append
+ * @buf: buffer to dump
+ * @len: number of bytes to dump
+ * @unit_len: add a space between every @unit_len bytes
+ * @block_len: add an extra space between every @block_len bytes
+ *
+ * Append @len bytes of @buf as hexadecimal into @str.
+ * Add spaces between every @unit_len and @block_len bytes.
+ * If @str is NULL, allocate a new string and return it;
+ * otherwise return @str.
  */
-#define QEMU_HEXDUMP_LINE_BYTES 16 /* Number of bytes to dump */
-#define QEMU_HEXDUMP_LINE_LEN 75   /* Number of characters in line */
-void qemu_hexdump_line(char *line, unsigned int b, const void *bufptr,
-                       unsigned int len, bool ascii);
+GString *qemu_hexdump_line(GString *str, const void *buf, size_t len,
+                           size_t unit_len, size_t block_len);
 
 /*
  * Hexdump a buffer to a file. An optional string prefix is added to every line