commit ae2b8dc8f0c87b30146c562464cae410a06fd7cd
author David Stevens <stevensd@google.com> Fri Apr 19 23:00:10 2019 +0000
committer CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> Fri Apr 19 23:00:10 2019 +0000
tree 4e164dfea7a40ecd479feb5924f795b6533a10c9
parent 99a97365a5e7e28f52a97703acded2abdf985111

[kernel][debug] Elide 0s in hexdump

If there are consecutive rows which are entirely 0s when dumping memory,
elide all rows except the first row and the last row if that last row is
also the last row that will be dumped.

Change-Id: I39c2769b61e3a250d41ae19cbd73e58613fa6405

zircon/kernel/lib/debug/debug.cpp

diff --git a/zircon/kernel/lib/debug/debug.cpp b/zircon/kernel/lib/debug/debug.cpp
index f5d8021..609c983 100644
--- a/zircon/kernel/lib/debug/debug.cpp
+++ b/zircon/kernel/lib/debug/debug.cpp
@@ -70,7 +70,8 @@
     addr_t address = (addr_t)ptr;
     size_t count;
 
-    for (count = 0; count < len; count += 16) {
+    int zero_line_count = 0;
+    for (count = 0; count < len; count += 16, address += 16) {
         union {
             uint32_t buf[4];
             uint8_t cbuf[16];
@@ -78,6 +79,24 @@
         size_t s = ROUNDUP(MIN(len - count, 16), 4);
         size_t i;
 
+        bool cur_line_zeros = true;
+        for (i = 0; i < s / 4; i++) {
+            cur_line_zeros &= (((const uint32_t*)address)[i] == 0);
+        }
+        if (cur_line_zeros) {
+            zero_line_count++;
+            if ((count + 16) >= len) {
+                // print the last line normally
+            } else if (zero_line_count >= 2) {
+                if (zero_line_count == 2) {
+                    pfn(".....\n");
+                }
+                continue;
+            }
+        } else {
+            zero_line_count = 0;
+        }
+
         pfn(((disp_addr + len) > 0xFFFFFFFF)
                 ? "0x%016llx: "
                 : "0x%08llx: ",
@@ -101,7 +120,6 @@
             }
         }
         pfn("|\n");
-        address += 16;
     }
 }
 
@@ -110,7 +128,26 @@
     size_t count;
     size_t i;
 
-    for (count = 0; count < len; count += 16) {
+    int zero_line_count = 0;
+    for (count = 0; count < len; count += 16, address += 16) {
+        bool cur_line_zeros = true;
+        for (i = 0; i < MIN(len - count, 16); i++) {
+            cur_line_zeros &= (((const uint8_t*)address)[i] == 0);
+        }
+        if (cur_line_zeros) {
+            zero_line_count++;
+            if ((count + 16) >= len) {
+                // print the last line normally
+            } else if (zero_line_count >= 2) {
+                if (zero_line_count == 2) {
+                    pfn(".....\n");
+                }
+                continue;
+            }
+        } else {
+            zero_line_count = 0;
+        }
+
         pfn(((disp_addr + len) > 0xFFFFFFFF)
                 ? "0x%016llx: "
                 : "0x%08llx: ",
@@ -132,7 +169,6 @@
         }
 
         pfn("\n");
-        address += 16;
     }
 }