From 5e0ee8e0b2a73c30a00f6f5a8dc6f697e8ceb0a1 Mon Sep 17 00:00:00 2001
From: Jakub Onderka <jakub.onderka@gmail.com>
Date: Wed, 1 Jan 2025 12:10:25 +0100
Subject: [PATCH] encoder: Optimise SIMD string escaping

---
 src/simdjson_encoder.cpp | 24 +++++++-------
 src/simdjson_encoder.h   | 69 +++++++++++++++++++++++++++++++++-------
 2 files changed, 69 insertions(+), 24 deletions(-)

diff --git a/src/simdjson_encoder.cpp b/src/simdjson_encoder.cpp
index 31a8a4f..1044564 100644
--- a/src/simdjson_encoder.cpp
+++ b/src/simdjson_encoder.cpp
@@ -474,38 +474,38 @@ static zend_always_inline size_t simdjson_append_escape(char *buf, const char c)
 template<typename T>
 static zend_always_inline void simdjson_escape_long_string(smart_str *buf, const char *s, size_t len)
 {
-	size_t i = 0;
     T chunk;
+    const char* start = s;
+    const size_t vlen = len & (int) (~(sizeof(chunk) - 1)); // max lenght that can be processed in chunk mode
     char *output;
 
-    // vlen = len - (len % sizeof(simdjson_vector8))
-	size_t vlen = len & (int) (~(sizeof(chunk) - 1));
-
 	output = simdjson_smart_str_alloc(buf, len + 2);
     *output++ = '"';
 
     // Iterate input string in chunks
-	for (; i < vlen; i += sizeof(chunk)) {
+	while (s < start + vlen) {
 		// Load chars to vector
-		chunk.load((const uint8_t *) &s[i]);
+		chunk.load((const uint8_t *) s);
 		// Check chunk if contains char that needs to be escaped
         auto needs_escaping = chunk.needs_escaping();
 		if (EXPECTED(!needs_escaping)) {
             // If no escape char found, store chunk in output buffer and move buffer pointer
 			chunk.store((uint8_t*)output);
             output += sizeof(chunk);
+            s += sizeof(chunk);
 		} else {
             // Allocate enought space for escaped chunk + space for rest of unescaped string
-            SIDMJSON_ZSTR_ALLOC(sizeof(chunk) * SIMDJSON_ENCODER_ESCAPE_LENGTH + (len - i));
+            SIDMJSON_ZSTR_ALLOC(sizeof(chunk) * SIMDJSON_ENCODER_ESCAPE_LENGTH + ((start + len) - s));
 
             // Copy first bytes that do not need escaping in chunk without checking
             auto j = chunk.escape_index(needs_escaping);
-            memcpy(output, &s[i], j);
+            memcpy(output, s, j);
             output += j;
+            s += j;
 
             // Process rest of chunk char by char and escape required char
             for (; j < sizeof(chunk); j++) {
-                char c = s[i + j];
+                char c = *s++;
                 if (EXPECTED(simdjson_need_escaping[(uint8_t)c] == 0)) {
                     *output++ = c;
                 } else {
@@ -515,12 +515,12 @@ static zend_always_inline void simdjson_escape_long_string(smart_str *buf, const
         }
 	}
 
-    // Ensure that buf contains enoug space that we can call unsafe methods
+    // Ensure that buf contains enough space that we can call unsafe methods
     SIDMJSON_ZSTR_ALLOC(sizeof(chunk) * SIMDJSON_ENCODER_ESCAPE_LENGTH + 1);
 
     // Finish last chars of string
-    for (; i < len; i++) {
-		char c = s[i];
+    while (s < start + len) {
+		char c = *s++;
 		if (EXPECTED(simdjson_need_escaping[(uint8_t)c] == 0)) {
 			*output++ = c;
 		} else {
diff --git a/src/simdjson_encoder.h b/src/simdjson_encoder.h
index 3b81312..66efd1d 100644
--- a/src/simdjson_encoder.h
+++ b/src/simdjson_encoder.h
@@ -80,18 +80,63 @@ static const _simdjson_escaped simdjson_escape[] = {
     {"", 0},
     {"", 0},
     {"\\\"", 2}, // 34
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, 
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, // 44
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, 
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, // 54
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, 
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, // 64
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, 
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, // 74
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, 
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, // 84
-    {"", 0}, {"", 0}, {"", 0}, {"", 0}, {"", 0}, 
-    {"", 0}, {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0}, // 44
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0}, // 54
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0}, // 64
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0}, // 74
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0}, // 84
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
+    {"", 0},
     {"\\\\", 2}, // 92
 };