add header to witness bin

c/main.cpp

@@ -118,6 +118,18 @@ void writeOutBin(Circom_CalcWit *ctx, std::string filename) {
 
     write_ptr = fopen(filename.c_str(),"wb");
 
+    // Add header
+    // 4 bytes --> total number of constraints
+    uint32_t witnessLength = _circuit.NVars;
+    // 4 bytes --> witness element size (measured in number of 32bit words)
+    uint32_t witnessSize = 8; // witness size = 8*32 = 256 bits
+    // 8bytes --> empty
+    uint64_t otherField = 0;
+
+    fwrite(&witnessLength, 4, 1, write_ptr);
+    fwrite(&witnessSize, 4, 1, write_ptr);
+    fwrite(&otherField, 8, 1, write_ptr);
+
     FrElement v;
 
     u8 buffOut[256];

doc/r1cs_bin_format.md

@@ -507,9 +507,9 @@ The format will be:
      ┣━━━━━━━━━━━━━━┫
      ┃ 03 00 00 00  ┃       nSections
      ┗━━━━━━━━━━━━━━┛
-     ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━┓
+     ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━┓
-     ┃ 01 00 00 00  ┃ 49 00 00 00 00 00 00 00  ┃      SectionType: Header
+     ┃ 01 00 00 00  ┃ 49 00 00 00 ┃      SectionType: Header
-     ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━━━━━━━━┛
+     ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━┛
         ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━┓
         ┃ 25 00 00 00  ┃ 10 00 00 00 ┃  FieldDefSize FieldDef
         ┣━━━━━━━━━━━━━━┻━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
@@ -531,9 +531,9 @@ The format will be:
         ┣━━━━━━━━━━━━━━┫
         ┃ 03 00 00 00  ┃    # Constraints
         ┗━━━━━━━━━━━━━━┛
-     ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━┓
+     ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━┓
-     ┃ 02 00 00 00  ┃ 8b 00 00 00 00 00 00 00 ┃      SectionType: Constraints
+     ┃ 02 00 00 00  ┃ 8b 00 00 00 ┃      SectionType: Constraints
-     ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━━━━━━━┛
+     ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━┛
         ┏━━━━━━━━━━━━━━┓   Constraint 0: (3w_5 + 8w_6) * (2w_0 + 20w_2 + 12w_3) - (5w_0 + 7w_2) = 0
         ┃ 02 00 00 00  ┃
         ┣━━━━━━━━━━━━━━╋━━━━━━━━┓
@@ -598,9 +598,9 @@ The format will be:
         ┃ 06 00 00 00  ┃  02 58 02   ┃
         ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━┛
 
-     ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━┓
+     ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━┓
-     ┃ 03 00 00 00  ┃ 1c 00 00 00 00 00 00 00 ┃      Wire to Label Map
+     ┃ 03 00 00 00  ┃ 1c 00 00 00 ┃      Wire to Label Map
-     ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━━━━━━━┛
+     ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━┛
         ┏━━━━━━━━━━━━━━┓
         ┃ 00 00 00 00  ┃
         ┣━━━━━━━━━━━━━━┫
@@ -624,7 +624,7 @@ And the binary representation in Hex:
 72 31 63 77
 01 00 00 00
 03 00 00 00
-01 00 00 00  49 00 00 00 00 00 00 00
+01 00 00 00  49 00 00 00
 25 00 00 00  10 00 00 00
 20 010000f0 93f5e143 9170b979 48e83328 5d588181 b64550b8 29a031e1 724e6430
 00 00 00 00
@@ -635,7 +635,7 @@ And the binary representation in Hex:
 03 00 00 00
 e8 03 00 00
 03 00 00 00
-02 00 00 00  8b 00 00 00 00 00 00 00
+02 00 00 00  8b 00 00 00
 02 00 00 00
 05 00 00 00  01 03
 06 00 00 00  01 08
@@ -662,7 +662,7 @@ e8 03 00 00
 03 00 00 00  01 05
 01 00 00 00
 06 00 00 00  02 58 02
-03 00 00 00  1c 00 00 00 00 00 00 00
+03 00 00 00  1c 00 00 00
 00 00 00 00
 03 00 00 00
 0a 00 00 00

src/r1csfile.js

@@ -31,7 +31,7 @@ async function loadR1cs(fileName, loadConstraints, loadMap) {
     let mapSize;
     for (let i=0; i<nSections; i++) {
         let ht = await readU32();
-        let hl = await readDouble64();
+        let hl = await readU32();
         if (ht == 1) {
             if (typeof pHeader != "undefined") assert(false, "File has two headder sections");
             pHeader = p;
@@ -114,15 +114,6 @@ async function loadR1cs(fileName, loadConstraints, loadMap) {
         return b.readInt32LE(0);
     }
 
-    async function readDouble64() {
-        const b = Buffer.allocUnsafe(8);
-        await fd.read(b, 0, 8, p);
-
-        p+=8;
-
-        return b.readDoubleLE(0);
-    }
-
     async function readBigInt() {
         const bl = Buffer.allocUnsafe(1);
         await fd.read(bl, 0, 1, p);
@@ -180,7 +171,7 @@ async function buildR1cs(ctx, fileName) {
     ///////////
     await writeU32(1); // Header type
     const pHeaderSize = p;
-    await writeDouble64(0); // Temporally set to 0 length
+    await writeU32(0); // Temporally set to 0 length
 
 
     // Field Def
@@ -207,13 +198,13 @@ async function buildR1cs(ctx, fileName) {
     await writeU32(ctx.signals.length);
     await writeU32(ctx.constraints.length);
 
-    const headerSize = p - pHeaderSize - 8;
+    const headerSize = p - pHeaderSize - 4;
 
     // Write constraints
     ///////////
     await writeU32(2); // Constraints type
     const pConstraintsSize = p;
-    await writeDouble64(0); // Temporally set to 0 length
+    await writeU32(0); // Temporally set to 0 length
 
     for (let i=0; i<ctx.constraints.length; i++) {
         if ((ctx.verbose)&&(i%10000 == 0)) {
@@ -223,13 +214,13 @@ async function buildR1cs(ctx, fileName) {
         await writeConstraint(ctx.constraints[i]);
     }
 
-    const constraintsSize = p - pConstraintsSize - 8;
+    const constraintsSize = p - pConstraintsSize - 4;
 
     // Write map
     ///////////
     await writeU32(3); // wires2label type
     const pMapSize = p;
-    await writeDouble64(0); // Temporally set to 0 length
+    await writeU32(0); // Temporally set to 0 length
 
 
     const arr = new Array(NWires);
@@ -247,13 +238,13 @@ async function buildR1cs(ctx, fileName) {
         if ((ctx.verbose)&&(i%100000)) console.log("writing label2wire map: ", i);
     }
 
-    const mapSize = p - pMapSize - 8;
+    const mapSize = p - pMapSize -4;
 
     // Write sizes
-    await writeDouble64(headerSize, pHeaderSize);
+    await writeU32(headerSize, pHeaderSize);
     await writeU32(fieldDefSize, pFieldDefSize);
-    await writeDouble64(constraintsSize, pConstraintsSize);
+    await writeU32(constraintsSize, pConstraintsSize);
-    await writeDouble64(mapSize, pMapSize);
+    await writeU32(mapSize, pMapSize);
 
     await fd.sync();
     await fd.close();
@@ -267,15 +258,6 @@ async function buildR1cs(ctx, fileName) {
         if (typeof(pos) == "undefined") p += 4;
     }
 
-    async function writeDouble64(v, pos) {
-        const b = Buffer.allocUnsafe(8);
-        b.writeDoubleLE(v);
-
-        await fd.write(b, 0, 8, pos);
-
-        if (typeof(pos) == "undefined") p += 8;
-    }
-
     async function writeConstraint(c) {
         await writeLC(c.a);
         await writeLC(c.b);