Delivers keichi#17 Add an option to set custom string padding char

Author: Ericbla

README.md

@@ -177,7 +177,10 @@ the following keys:
 - `trim` - (Optional, default to `false`) If true, then trim() (remove leading and trailing spaces)
   the parsed string.
 - `padding` - (Optional, Only used for encoding, default to `right`) If `left` then the string
-  will be right aligned (padding left with leading spaces) depending of the `length` option
+  will be right aligned (padding left with `padd` char or space) depending of the `length` option
+- `padd` - (Optional, Only used for encoding with `length` specified) A string  from which first character (1 Byte)
+  is used as a padding char if necessary (provided string length is less than `length` option). Note: Only 'ascii'
+  or utf8 < 0x80  are alowed (fallback to 'space' padding else).
 
 ### buffer(name[, options])
 Parse bytes as a buffer. `name` should consist only of alpha numeric

lib/binary_parser.js

@@ -782,20 +782,31 @@ Parser.prototype.generate_encodeString = function(ctx) {
     // Compute padding length
     var padLen = ctx.generateTmpVariable();
     ctx.pushCode("{0} = {1} - {2}.length;", padLen, optLength, tmpBuf);
+    var padCharVar = ctx.generateTmpVariable();
+    var padChar = " ";
+    if (this.options.padd && typeof this.options.padd === "string") {
+      var code = this.options.padd.charCodeAt(0);
+      if (code < 0x80) {
+        padChar = String.fromCharCode(code);
+      }
+    }
+    ctx.pushCode('{0} = "{1}";', padCharVar, padChar);
     if (this.options.padding === "left") {
       // Add heading padding spaces
       ctx.pushCode(
-        "if ({0} > 0) {smartBuffer.writeString(' '.repeat({0}));}",
-        padLen
+        "if ({0} > 0) {smartBuffer.writeString({1}.repeat({0}));}",
+        padLen,
+        padCharVar
       );
     }
     // Copy the temporary string buffer to current smartBuffer
     ctx.pushCode("smartBuffer.writeBuffer({0});", tmpBuf);
     if (this.options.padding !== "left") {
       // Add trailing padding spaces
       ctx.pushCode(
-        "if ({0} > 0) {smartBuffer.writeString(' '.repeat({0}));}",
-        padLen
+        "if ({0} > 0) {smartBuffer.writeString({1}.repeat({0}));}",
+        padLen,
+        padCharVar
       );
     }
   } else {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "binary-parser-encoder",
-  "version": "1.4.3",
+  "version": "1.4.4",
   "description": "Blazing-fast binary parser builder",
   "main": "lib/binary_parser.js",
   "devDependencies": {

test/yy_primitive_encoder.js

@@ -374,6 +374,39 @@ describe("Primitive encoder", function() {
       encoded = parser.encode({ a: "abcdefgh" });
       assert.deepEqual(encoded, Buffer.from("abcdef"));
     });
+    it("should encode string with right padding and provided padding char", function() {
+      var parser = Parser.start().string("a", { length: 6, padd: "x" });
+      var encoded = parser.encode({ a: "abcd" });
+      assert.deepEqual(encoded, Buffer.from("abcdxx"));
+      encoded = parser.encode({ a: "abcdefgh" });
+      assert.deepEqual(encoded, Buffer.from("abcdef"));
+    });
+    it("should encode string with left padding and provided padding char", function() {
+      var parser = Parser.start().string("a", {
+        length: 6,
+        padding: "left",
+        padd: "."
+      });
+      var encoded = parser.encode({ a: "abcd" });
+      assert.deepEqual(encoded, Buffer.from("..abcd"));
+      encoded = parser.encode({ a: "abcdefgh" });
+      assert.deepEqual(encoded, Buffer.from("abcdef"));
+    });
+    it("should encode string with padding and padding char 0", function() {
+      var parser = Parser.start().string("a", { length: 6, padd: "\u0000" });
+      var encoded = parser.encode({ a: "abcd" });
+      assert.deepEqual(encoded, Buffer.from("abcd\u0000\u0000"));
+    });
+    it("should encode string with padding and first byte of padding char", function() {
+      var parser = Parser.start().string("a", { length: 6, padd: "1234" });
+      var encoded = parser.encode({ a: "abcd" });
+      assert.deepEqual(encoded, Buffer.from("abcd11"));
+    });
+    it("should encode string with space padding when padd char is not encoded on 1 Byte", function() {
+      var parser = Parser.start().string("a", { length: 6, padd: "こ" });
+      var encoded = parser.encode({ a: "abcd" });
+      assert.deepEqual(encoded, Buffer.from("abcd  "));
+    });
   });
 
   describe("Buffer encoder", function() {