Implement user specified require of modules.

Closes #375.

constants.js

@@ -1,7 +1,7 @@
 // Node.js API.
 const util = require('util')
 
-// Format source code maintaining indents.
+// Format source code maintaining indentation.
 const $ = require('programmatic')
 
 function generate (packet) {

inliner.js

@@ -1,4 +1,4 @@
-// Format source code maintaining indents.
+// Format source code maintaining indentation.
 const $ = require('programmatic')
 
 //

parse.all.js

@@ -1,15 +1,33 @@
-const join = require('./join')
-const map = require('./map')
-const snuggle = require('./snuggle')
-const unpack = require('./unpack')
-const unsign = require('./fiddle/unsign')
+// Format source code maintaining indentation.
 const $ = require('programmatic')
+
+// Generate literal object construction.
 const vivify = require('./vivify')
+
+// Generate two's compliment conversion.
+const unsign = require('./fiddle/unsign')
+
+// Generate integer unpacking.
+const unpack = require('./unpack')
+
+// Maintain a set of lookup constants.
 const lookup = require('./lookup')
 
 // Generate inline function source.
 const inliner = require('./inliner')
 
+// Generate required modules and functions.
+const required = require('./required')
+
+const map = require('./map')
+
+// Format source code maintaining indentation.
+const join = require('./join')
+
+// Join an array of strings with first line of subsequent element catenated to
+// last line of previous element.
+const snuggle = require('./snuggle')
+
 function expand (fields) {
     const expanded = []
     for (const field of fields) {
@@ -52,7 +70,7 @@ function expand (fields) {
     return expanded
 }
 
-function generate (packet, bff) {
+function generate (packet, { require, bff }) {
     let $i = -1, $I = -1, $sip = -1, $step = 1
 
     const variables = { packet: true, step: true }
@@ -521,40 +539,51 @@ function generate (packet, bff) {
     const lookups = Object.keys($lookup).length != 0
                   ? `const $lookup = ${JSON.stringify($lookup, null, 4)}`
                   : null
+
+    const requires = required(require)
+
     if (bff) {
         return $(`
             parsers.bff.${packet.name} = function () {
+                `, requires, -1, `
+
                 `, lookups, -1, `
 
-                return function parse ($buffer, $start, $end) {
-                    `, lets.length ? `let ${lets.join(', ')}` : null, -1, `
+                return function () {
+                    return function parse ($buffer, $start, $end) {
+                        `, lets.length ? `let ${lets.join(', ')}` : null, -1, `
 
-                    `, vivify.structure(`const ${packet.name}`, packet), `
+                        `, vivify.structure(`const ${packet.name}`, packet), `
 
-                    `, source, `
+                        `, source, `
 
-                    return { start: $start, object: object, parse: null }
-                }
+                        return { start: $start, object: object, parse: null }
+                    }
+                } ()
             }
         `)
     }
 
     return $(`
-        parsers.all.${packet.name} = function ($buffer, $start) {
+        parsers.all.${packet.name} = function () {
+            `, requires, -1, `
+
             `, lookups, -1, `
 
-            `, lets.length ? `let ${lets.join(', ')}` : null, -1, `
+            return function ($buffer, $start) {
+                `, lets.length ? `let ${lets.join(', ')}` : null, -1, `
 
-            `, 'const ' + vivify.structure(packet.name, packet), `
+                `, 'const ' + vivify.structure(packet.name, packet), `
 
-            `, source, `
+                `, source, `
 
-            return ${packet.name}
-        }
+                return ${packet.name}
+            }
+        } ()
     `)
 }
 
 module.exports = function (definition, options = {}) {
     const expanded = expand(JSON.parse(JSON.stringify(definition)))
-    return join(expanded.map(packet => generate(packet, options.bff)))
+    return join(expanded.map(packet => generate(packet, options)))
 }

parse.inc.js

@@ -1,16 +1,34 @@
-const join = require('./join')
-const map = require('./map')
-const snuggle = require('./snuggle')
-const unpack = require('./unpack')
-const unsign = require('./fiddle/unsign')
+// Format source code maintaining indentation.
 const $ = require('programmatic')
+
+// Generate literal object construction.
 const vivify = require('./vivify')
+
+// Generate two's compliment conversion.
+const unsign = require('./fiddle/unsign')
+
+// Generate integer unpacking.
+const unpack = require('./unpack')
+
+// Maintain a set of lookup constants.
 const lookup = require('./lookup')
 
 // Generate inline function source.
 const inliner = require('./inliner')
 
-function generate (packet) {
+// Generate required modules and functions.
+const required = require('./required')
+
+const map = require('./map')
+
+// Format source code maintaining indentation.
+const join = require('./join')
+
+// Join an array of strings with first line of subsequent element catenated to
+// last line of previous element.
+const snuggle = require('./snuggle')
+
+function generate (packet, { require = null }) {
     let $step = 0, $i = -1, $sip = -1, iterate = false, _terminated = false, surround = false
 
     const variables = { packet: true, step: true }
@@ -515,21 +533,29 @@ function generate (packet) {
     }
 
     const object = `parsers.inc.${packet.name}`
+
     const lookups = Object.keys($lookup).length != 0
                   ? `const $lookup = ${JSON.stringify($lookup, null, 4)}`
                   : null
+
+    const requires = required(require)
+
     return $(`
-        ${object} = function (${signature.join(', ')}) {
+        parsers.inc.${packet.name} = function () {
+            `, requires, -1, `
+
             `, lookups, -1, `
 
-            let $_, $bite
-            return function parse ($buffer, $start, $end) {
-                `, source, `
+            return function (${signature.join(', ')}) {
+                let $_, $bite
+                return function parse ($buffer, $start, $end) {
+                    `, source, `
+                }
             }
-        }
+        } ()
     `)
 }
 
-module.exports = function (definition) {
-    return join(JSON.parse(JSON.stringify(definition)).map(packet => generate(packet)))
+module.exports = function (definition, options) {
+    return join(JSON.parse(JSON.stringify(definition)).map(packet => generate(packet, options)))
 }

required.js

@@ -0,0 +1,16 @@
+// Node.js API.
+const util = require('util')
+
+module.exports = function (required) {
+    return required != null
+        ? Object.keys(required).map(name => {
+            for (const name in required) {
+                switch (typeof required[name]) {
+                case 'function':
+                    return `const ${name} = null`
+                case 'string':
+                    return `const ${name} = require(${util.inspect(required[name])})`
+                }
+            }
+        }).join('\n') : null
+}

serialize.all.js

@@ -1,13 +1,32 @@
-const join = require('./join')
 const map = require('./map')
-const lookup = require('./lookup')
-const snuggle = require('./snuggle')
+
+// Generate integer packing.
 const pack = require('./pack')
+
+// Maintain a set of lookup constants.
+const lookup = require('./lookup')
+
+// Format source code maintaining indentation.
 const $ = require('programmatic')
 
 // Generate inline function source.
 const inliner = require('./inliner')
 
+// Generate required modules and functions.
+const required = require('./required')
+
+// Format source code maintaining indentation.
+const join = require('./join')
+
+// Join an array of strings with first line of subsequent element catenated to
+// last line of previous element.
+const snuggle = require('./snuggle')
+
+//
+
+// Add implicit field definitions to the given array of field definitions.
+
+//
 function expand (fields) {
     const expanded = []
     for (const field of fields) {
@@ -123,7 +142,7 @@ function checkpoints (path, fields, index = 0) {
     })
 }
 
-function generate (packet, bff) {
+function generate (packet, { require = null, bff }) {
     let $step = 0, $i = -1, $$ = -1
 
     const variables = { packet: true, step: true }
@@ -432,20 +451,27 @@ function generate (packet, bff) {
     const lookups = Object.keys($lookup).length != 0
                   ? `const $lookup = ${JSON.stringify($lookup, null, 4)}`
                   : null
+
+    const requires = required(require)
+
     return $(`
-        serializers.${bff ? 'bff' : 'all'}.${packet.name} = function (${packet.name}) {
+        serializers.${bff ? 'bff' : 'all'}.${packet.name} = function () {
+            `, requires, -1, `
+
             `, lookups, -1, `
 
-            return function ($buffer, $start, $end) {
-                `, consts.length != 0 ? `const ${consts.join(', ')}` : null, -1, `
+            return function (${packet.name}) {
+                return function ($buffer, $start, $end) {
+                    `, consts.length != 0 ? `const ${consts.join(', ')}` : null, -1, `
 
-                `, lets.length != 0 ? `let ${lets.join(', ')}` : null, -1, `
+                    `, lets.length != 0 ? `let ${lets.join(', ')}` : null, -1, `
 
-                `, source, `
+                    `, source, `
 
-                return { start: $start, serialize: null }
+                    return { start: $start, serialize: null }
+                }
             }
-        }
+        } ()
     `)
 }
 
@@ -455,6 +481,6 @@ module.exports = function (definition, options = {}) {
         if (options.bff) {
             packet.fields = checkpoints(packet.name, packet.fields)
         }
-        return generate(packet, options.bff)
+        return generate(packet, options)
     }))
 }