util/hexdump: introduce qemu_hexdump_line()

Dumping one line of hexadecimal/ASCII from a buffer is often needed.
Move this part from qemu_hexdump() and use it

Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20200925091055.186023-2-lvivier@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 42 insertions, 20 deletions

diff --git a/include/qemu-common.h b/include/qemu-common.h
index 9cfd626..cc902b6 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -135,6 +135,14 @@ char *os_find_datadir(void);
 int os_parse_cmd_args(int index, const char *optarg);
 
 /*
+ * Hexdump a line of a byte buffer into a hexadecimal/ASCII buffer
+ */
+#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);
+
+/*
  * Hexdump a buffer to a file. An optional string prefix is added to every line
  */
 
diff --git a/util/hexdump.c b/util/hexdump.c
index 0b4662e..2c105a8 100644
--- a/util/hexdump.c
+++ b/util/hexdump.c
@@ -16,36 +16,50 @@
 #include "qemu/osdep.h"
 #include "qemu-common.h"
 
-void qemu_hexdump(FILE *fp, const char *prefix,
-                  const void *bufptr, size_t size)
+void qemu_hexdump_line(char *line, unsigned int b, const void *bufptr,
+                       unsigned int len, bool ascii)
 {
     const char *buf = bufptr;
-    unsigned int b, len, i, c;
+    int i, c;
 
-    for (b = 0; b < size; b += 16) {
-        len = size - b;
-        if (len > 16) {
-            len = 16;
+    if (len > QEMU_HEXDUMP_LINE_BYTES) {
+        len = QEMU_HEXDUMP_LINE_BYTES;
+    }
+
+    line += snprintf(line, 6, "%04x:", b);
+    for (i = 0; i < QEMU_HEXDUMP_LINE_BYTES; i++) {
+        if ((i % 4) == 0) {
+            *line++ = ' ';
         }
-        fprintf(fp, "%s: %04x:", prefix, b);
-        for (i = 0; i < 16; i++) {
-            if ((i % 4) == 0) {
-                fprintf(fp, " ");
-            }
-            if (i < len) {
-                fprintf(fp, " %02x", (unsigned char)buf[b + i]);
-            } else {
-                fprintf(fp, "   ");
-            }
+        if (i < len) {
+            line += sprintf(line, " %02x", (unsigned char)buf[b + i]);
+        } else {
+            line += sprintf(line, "   ");
         }
-        fprintf(fp, " ");
+    }
+    if (ascii) {
+        *line++ = ' ';
         for (i = 0; i < len; i++) {
             c = buf[b + i];
             if (c < ' ' || c > '~') {
                 c = '.';
             }
-            fprintf(fp, "%c", c);
+            *line++ = c;
         }
-        fprintf(fp, "\n");
     }
+    *line = '\0';
+}
+
+void qemu_hexdump(FILE *fp, const char *prefix,
+                  const void *bufptr, size_t size)
+{
+    unsigned int b, len;
+    char line[QEMU_HEXDUMP_LINE_LEN];
+
+    for (b = 0; b < size; b += QEMU_HEXDUMP_LINE_BYTES) {
+        len = size - b;
+        qemu_hexdump_line(line, b, bufptr, len, true);
+        fprintf(fp, "%s: %s\n", prefix, line);
+    }
+
 }