From e1e92fea92ed80dd10ff0cb325433a97c1826b6a Mon Sep 17 00:00:00 2001
From: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Date: Sat, 2 May 2026 15:39:55 +0000
Subject: [PATCH] patch 9.2.0431: blob encoding can be improved
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Problem:  blob encoding can be improved
Solution: Speed up blob encoding by avoiding per-byte ga_append()
          (Yasuhiro Matsumoto)

Replace the per-byte ga_append loop in the VAR_BLOB branch of
json_encode_item() with a single ga_grow for the worst case
(2 + 4 * blen) and direct writes through a local pointer. Also
read blob bytes through a local char_u* instead of going through
blob_get() for each byte.

Benchmark (1 MiB blob, 5 iterations, total seconds, median of 3 runs):

| byte distribution | Before | After | Speedup |
|---|---:|---:|---:|
| 1-digit (0–9)     | 0.0254 | 0.0174 | 1.46x |
| 2-digit (10–99)   | 0.0344 | 0.0064 | 5.38x |
| 3-digit (100–255) | 0.0539 | 0.0102 | 5.28x |
| mixed (0–255)     | 0.0335 | 0.0093 | 3.60x |

closes: #20113

Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/json.c    | 33 +++++++++++++++++++++------------
 src/version.c |  2 ++
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/src/json.c b/src/json.c
index b0d98a290e..a3e58043d8 100644
--- a/src/json.c
+++ b/src/json.c
@@ -369,29 +369,38 @@ json_encode_item(garray_T *gap, typval_T *val, int copyID, int options)
 		GA_CONCAT_LITERAL(gap, "[]");
 	    else
 	    {
-		ga_append(gap, '[');
-		for (i = 0; i < b->bv_ga.ga_len; i++)
+		int	blen = b->bv_ga.ga_len;
+		char_u	*src;
+		char_u	*dst;
+
+		// Worst case: '[' + ']' + per-byte 3 digits + comma = 2 + 4*blen
+		if (ga_grow(gap, 2 + 4 * blen) == FAIL)
+		    goto theend;
+		src = (char_u *)b->bv_ga.ga_data;
+		dst = (char_u *)gap->ga_data + gap->ga_len;
+		*dst++ = '[';
+		for (i = 0; i < blen; i++)
 		{
-		    int	    byte = blob_get(b, i);
+		    int	    byte = src[i];
 
 		    if (i > 0)
-			ga_append(gap, ',');
-		    // blob bytes are 0-255, use simple conversion
+			*dst++ = ',';
 		    if (byte >= 100)
 		    {
-			ga_append(gap, '0' + byte / 100);
-			ga_append(gap, '0' + (byte / 10) % 10);
-			ga_append(gap, '0' + byte % 10);
+			*dst++ = '0' + byte / 100;
+			*dst++ = '0' + (byte / 10) % 10;
+			*dst++ = '0' + byte % 10;
 		    }
 		    else if (byte >= 10)
 		    {
-			ga_append(gap, '0' + byte / 10);
-			ga_append(gap, '0' + byte % 10);
+			*dst++ = '0' + byte / 10;
+			*dst++ = '0' + byte % 10;
 		    }
 		    else
-			ga_append(gap, '0' + byte);
+			*dst++ = '0' + byte;
 		}
-		ga_append(gap, ']');
+		*dst++ = ']';
+		gap->ga_len = (int)(dst - (char_u *)gap->ga_data);
 	    }
 	    break;
 
diff --git a/src/version.c b/src/version.c
index 0ce32fb2e4..9208a50785 100644
--- a/src/version.c
+++ b/src/version.c
@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    431,
 /**/
     430,
 /**/