x.json2: optimise encoding to be faster than cJSON with -prod (#20052)

cmd/tools/vls.v

@@ -113,7 +113,13 @@ fn (upd VlsUpdater) update_manifest(new_path string, from_source bool, timestamp
 	manifest['last_updated'] = json2.Any(timestamp.format_ss())
 	manifest['from_source'] = json2.Any(from_source)
 
-	json_enc.encode_value(manifest, mut manifest_file)!
+	mut buffer := []u8{}
+
+	json_enc.encode_value(manifest, mut buffer)!
+
+	manifest_file.write(buffer)!
+
+	unsafe { buffer.free() }
 }
 
 fn (upd VlsUpdater) init_download_prebuilt() ! {

vlib/v/gen/c/cgen.v

@@ -5524,7 +5524,12 @@ fn (mut g Gen) const_decl_precomputed(mod string, name string, field_name string
 					return false
 				}
 				escval := util.smart_quote(u8(rune_code).ascii_str(), false)
-				g.const_decl_write_precomputed(mod, styp, cname, field_name, "'${escval}'")
+
+				g.global_const_defs[util.no_dots(field_name)] = GlobalConstDef{
+					mod: mod
+					def: "#define ${cname} '${escval}'"
+					order: -1
+				}
 			} else {
 				g.const_decl_write_precomputed(mod, styp, cname, field_name, u32(ct_value).str())
 			}

vlib/v/tests/bench/bench_json_vs_json2.v

@@ -5,8 +5,8 @@ import time
 import benchmark
 
 // recommendations:
-// MAX_ITERATIONS=90_000 ./v run vlib/v/tests/bench/bench_json_vs_json2.v
-// MAX_ITERATIONS=90_000 ./v -no-bounds-checking -prod -cc clang-15 crun vlib/v/tests/bench/bench_json_vs_json2.v
+// MAX_ITERATIONS=100_000 ./v run vlib/v/tests/bench/bench_json_vs_json2.v
+// MAX_ITERATIONS=100_000 ./v -no-bounds-checking -prod -cc clang-15 crun vlib/v/tests/bench/bench_json_vs_json2.v
 
 const max_iterations = os.getenv_opt('MAX_ITERATIONS') or { '1000' }.int()
 
@@ -77,7 +77,7 @@ fn benchmark_measure_json_vs_json2_on_complex_struct() ! {
 			return error('json.decode ${p}')
 		}
 	}
-	b.measure('json.decode')
+	b.measure('json.decode\n')
 
 	measure_json_encode_old_vs_new(json.decode(Person, s)!)!
 }
@@ -124,7 +124,7 @@ fn benchmark_measure_decode_by_type() ! {
 			return error('json.decode ${d}')
 		}
 	}
-	b.measure(' json.decode StructType[string]')
+	b.measure(' json.decode StructType[string]\n')
 
 	vb := '{"val": true}'
 	for _ in 0 .. max_iterations {
@@ -140,7 +140,7 @@ fn benchmark_measure_decode_by_type() ! {
 			return error('json.decode ${d}')
 		}
 	}
-	b.measure(' json.decode StructType[bool]')
+	b.measure(' json.decode StructType[bool]\n')
 
 	v0 := '{"val": 0}'
 	for _ in 0 .. max_iterations {
@@ -156,7 +156,7 @@ fn benchmark_measure_decode_by_type() ! {
 			return error('json.decode ${d}')
 		}
 	}
-	b.measure(' json.decode StructType[int]')
+	b.measure(' json.decode StructType[int]\n')
 
 	vt := '{"val": "2015-01-06 15:47:32"}'
 	for _ in 0 .. max_iterations {
@@ -172,7 +172,7 @@ fn benchmark_measure_decode_by_type() ! {
 			return error('json2.decode ${d}')
 		}
 	}
-	b.measure(' json.decode StructType[time.Time]')
+	b.measure(' json.decode StructType[time.Time]\n')
 }
 
 fn measure_json_encode_old_vs_new[T](val T) ! {
@@ -191,5 +191,5 @@ fn measure_json_encode_old_vs_new[T](val T) ! {
 			return error('json.encode ${e}')
 		}
 	}
-	b.measure(' json.encode ${typename}')
+	b.measure(' json.encode ${typename}\n')
 }

vlib/x/json2/README.md

@@ -150,3 +150,18 @@ The following list shows the possible outputs when casting a value to an incompa
 3. Casting non-string values to string (`str()`) will return the
 JSON string representation of the value.
 4. Casting non-numeric values to int/float (`int()`/`i64()`/`f32()`/`f64()`) will return zero.
+
+## Encoding using string builder instead of []u8
+To be more performant, `json2`, in PR 20052, decided to use buffers directly instead of Writers.
+If you want to use Writers you can follow the steps below:
+
+```v ignore
+mut sb := strings.new_builder(64)
+mut buffer := []u8{}
+
+json2.encode_value(<some value to be encoded here>, mut buffer)!
+
+sb.write(buffer)!
+
+unsafe { buffer.free() }
+```

vlib/x/json2/encode_struct_test.v

@@ -229,19 +229,19 @@ fn test_alias() {
 
 fn test_pointer() {
 	mut string_initialized_with_reference := ''
-	assert json.encode(StructTypePointer[string]{ val: 0 }) == '{}'
+	assert json.encode(StructTypePointer[string]{ val: unsafe { nil } }) == '{}'
 	assert json.encode(StructTypePointer[string]{ val: &string_initialized_with_reference }) == '{"val":""}'
 	string_initialized_with_reference = 'a'
 	assert json.encode(StructTypePointer[string]{ val: &string_initialized_with_reference }) == '{"val":"a"}'
 
 	mut bool_initialized_with_reference := false
-	assert json.encode(StructTypePointer[bool]{ val: 0 }) == '{}'
+	assert json.encode(StructTypePointer[bool]{ val: unsafe { nil } }) == '{}'
 	assert json.encode(StructTypePointer[bool]{ val: &bool_initialized_with_reference }) == '{"val":false}'
 	bool_initialized_with_reference = true
 	assert json.encode(StructTypePointer[bool]{ val: &bool_initialized_with_reference }) == '{"val":true}'
 
 	mut int_initialized_with_reference := 0
-	assert json.encode(StructTypePointer[int]{ val: 0 }) == '{}'
+	assert json.encode(StructTypePointer[int]{ val: unsafe { nil } }) == '{}'
 	assert json.encode(StructTypePointer[int]{ val: &int_initialized_with_reference }) == '{"val":0}'
 	int_initialized_with_reference = 1
 	assert json.encode(StructTypePointer[int]{ val: &int_initialized_with_reference }) == '{"val":1}'