stream stringify

README.md

@@ -118,7 +118,8 @@ const fastJson = require('fast-json-stringify')
 const stringify = fastJson(mySchema, {
   schema: { ... },
   ajv: { ... },
-  rounding: 'ceil'
+  rounding: 'ceil',
+  enableStream: false
 })
 ```
 
@@ -127,6 +128,7 @@ const stringify = fastJson(mySchema, {
 - `rounding`: setup how the `integer` types will be rounded when not integers. [More details](#integer)
 - `largeArrayMechanism`: set the mechanism that should be used to handle large
 (by default `20000` or more items) arrays. [More details](#largearrays)
+- `enableStream`: write the json on a stream [More details](#stream)
 
 
 <a name="api"></a>
@@ -648,6 +650,37 @@ const stringify = fastJson({
 })
 ```
 
+<a name="stream"></a>
+#### stream
+You can set specific a stream to write
+Example:
+```javascript
+const fastJson = require('fast-json-stringify')
+
+const schema = {
+  title: 'Example Schema',
+  type: 'object',
+  properties: {
+    foo: {
+      type: 'string'
+    }
+}
+const stringify = fastJson(schema, { enableStream: true })
+
+const data = { foo: 'bar' }
+const stream = new Readable()
+stringify(data, stream);
+
+const chunks = []
+stream.on('data', (chunk) => {
+  const str = Buffer.from(chunk).toString('utf8')
+  console.log('chunk', str)
+  chunks.push(str)
+})
+stream.on('end', () => console.log(chunks.join('')))
+```
+
+
 ##### Benchmarks
 
 For reference, here goes some benchmarks for comparison over the three

index.js

@@ -155,9 +155,14 @@ function build (schema, options) {
     `
   } else {
     contextFunctionCode = `
-    function main (input) {
+    let stream
+    function main (input, _stream) {
+      stream = _stream
       let json = ''
       ${code}
+      if( stream ){
+        stream.push(null)
+      }
       return json
     }
     ${context.functions.join('\n')}
@@ -263,7 +268,7 @@ function buildExtraObjectPropertiesSerializer (context, location, addComma) {
   const schema = location.schema
   const propertiesKeys = Object.keys(schema.properties || {})
 
-  let code = `
+  let code = `/** begin buildExtraObjectPropertiesSerializer */
     const propertiesKeys = ${JSON.stringify(propertiesKeys)}
     for (const [key, value] of Object.entries(obj)) {
       if (
@@ -313,6 +318,8 @@ function buildExtraObjectPropertiesSerializer (context, location, addComma) {
 
   code += `
     }
+
+    /** end buildExtraObjectPropertiesSerializer */
   `
   return code
 }
@@ -333,7 +340,9 @@ function buildInnerObject (context, location) {
   )
   const hasRequiredProperties = requiredProperties.includes(propertiesKeys[0])
 
-  let code = 'let value\n'
+  let code = `/** begin buildInnerObject */
+  let value
+  `
 
   for (const key of requiredProperties) {
     if (!propertiesKeys.includes(key)) {
@@ -363,9 +372,16 @@ function buildInnerObject (context, location) {
       value = obj[${sanitizedKey}]
       if (value !== undefined) {
         ${addComma}
-        json += ${JSON.stringify(sanitizedKey + ':')}
-        ${buildValue(context, propertyLocation, 'value')}
-      }`
+        json += ${JSON.stringify(sanitizedKey + ':')}`
+    if (context.options.enableStream) {
+      code += `
+        stream.push(json)
+        json = '';
+      `
+    }
+    code += `  
+      ${buildValue(context, propertyLocation, 'value')}
+    }`
 
     if (defaultValue !== undefined) {
       code += ` else {
@@ -392,7 +408,21 @@ function buildInnerObject (context, location) {
   }
 
   code += `
-    return json + '}'
+      json += '}'
+  `
+
+  if (context.options.enableStream) {
+    code += `
+      if( json ){
+        stream.push(json)
+        json = ''
+      }
+    `
+  }
+
+  code += `
+     return json
+    /** end buildInnerObject */
   `
   return code
 }
@@ -476,6 +506,7 @@ function buildObject (context, location) {
   }
 
   let functionCode = `
+    /** begin buildObject */
   `
 
   const nullable = schema.nullable === true
@@ -487,6 +518,8 @@ function buildObject (context, location) {
 
       ${buildInnerObject(context, location)}
     }
+
+    /** end buildObject */
   `
 
   context.functions.push(functionCode)
@@ -518,13 +551,15 @@ function buildArray (context, location) {
   }
 
   let functionCode = `
+    /** begin buildArray */
+
     function ${functionName} (obj) {
       // ${schemaRef}
   `
 
   const nullable = schema.nullable === true
   functionCode += `
-    ${!nullable ? 'if (obj === null) return \'[]\'' : ''}
+    ${!nullable ? `if (obj === null) return ${context.options.enableStream ? 'stream.push(\'[]\')' : '\'[]\''}` : ''}
     if (!Array.isArray(obj)) {
       throw new TypeError(\`The value of '${schemaRef}' does not match schema definition.\`)
     }
@@ -540,19 +575,36 @@ function buildArray (context, location) {
   }
 
   if (largeArrayMechanism === 'json-stringify') {
-    functionCode += `if (arrayLength && arrayLength >= ${largeArraySize}) return JSON.stringify(obj)\n`
+    functionCode += `if (arrayLength && arrayLength >= ${largeArraySize}) return ${context.options.enableStream ? 'stream.push(JSON.stringify(obj))' : 'JSON.stringify(obj)'}\n`
+  }
+
+  if (context.options.enableStream) {
+    functionCode += `
+      stream.push('[')
+    `
   }
 
   functionCode += `
     let value
     let jsonOutput = ''
   `
 
+  let codePushLoop = ''
+  if (context.options.enableStream) {
+    codePushLoop = `
+      if( jsonOutput ){
+        stream.push(jsonOutput)
+        jsonOutput = ''
+      }
+    `
+  }
+
   if (Array.isArray(itemsSchema)) {
     for (let i = 0; i < itemsSchema.length; i++) {
       const item = itemsSchema[i]
       functionCode += `value = obj[${i}]`
       const tmpRes = buildValue(context, itemsLocation.getPropertyLocation(i), 'value')
+
       functionCode += `
         if (${i} < arrayLength) {
           if (${buildArrayTypeCondition(item.type, `[${i}]`)}) {
@@ -576,6 +628,7 @@ function buildArray (context, location) {
           if (i < arrayLength - 1) {
             jsonOutput += ','
           }
+          ${codePushLoop}
         }`
     }
   } else {
@@ -588,12 +641,25 @@ function buildArray (context, location) {
         if (i < arrayLength - 1) {
           jsonOutput += ','
         }
+        ${codePushLoop}
       }`
   }
 
+  if (context.options.enableStream) {
+    functionCode += `
+      stream.push(']')
+      return ''
+    `
+  } else {
+    functionCode += `
+      return \`[\${jsonOutput}]\`
+    `
+  }
+
   functionCode += `
-    return \`[\${jsonOutput}]\`
-  }`
+    }
+    /** end buildArray */
+  `
 
   context.functions.push(functionCode)
   return functionName
@@ -650,7 +716,9 @@ function buildMultiTypeSerializer (context, location, input) {
   const schema = location.schema
   const types = schema.type.sort(t1 => t1 === 'null' ? -1 : 1)
 
-  let code = ''
+  let code = `
+    /** begin buildMultiTypeSerializer */
+  `
 
   types.forEach((type, index) => {
     location.schema = { ...location.schema, type }
@@ -710,6 +778,8 @@ function buildMultiTypeSerializer (context, location, input) {
   }
   code += `
     else throw new TypeError(\`The value of '${schemaRef}' does not match schema definition.\`)
+
+    /** end buildMultiTypeSerializer */
   `
 
   return code
@@ -980,7 +1050,7 @@ function buildValue (context, location, input) {
     }
   }
 
-  let code = ''
+  let code = '\n/** begin buildValue */\n'
 
   const type = schema.type
   const nullable = schema.nullable === true
@@ -993,19 +1063,25 @@ function buildValue (context, location, input) {
   }
 
   if (schema.const !== undefined) {
+    code += '\n/** begin buildConstSerializer */\n'
     code += buildConstSerializer(location, input)
+    code += '\n/** end buildConstSerializer */\n'
   } else if (Array.isArray(type)) {
+    code += '\n/** begin buildMultiTypeSerializer */\n'
     code += buildMultiTypeSerializer(context, location, input)
+    code += '\n/** end buildMultiTypeSerializer */\n'
   } else {
+    code += '\n/** begin buildSingleTypeSerializer */\n'
     code += buildSingleTypeSerializer(context, location, input)
+    code += '\n/** end buildSingleTypeSerializer */\n'
   }
 
   if (nullable) {
     code += `
       }
     `
   }
-
+  code += '\n/** end buildValue */\n'
   return code
 }