Add remoteContiguousLength field to hints

To support holepunchto/hypercore#743 persisting
`remoteContiguousLength`.

Author: lejeunerenard

build.js

@@ -286,6 +286,10 @@ core.register({
     {
       name: 'contiguousLength',
       type: 'uint'
+    },
+    {
+      name: 'remoteContiguousLength',
+      type: 'uint'
     }
   ]
 })

spec/hyperschema/index.js

@@ -397,22 +397,27 @@ const encoding12 = {
 // @core/hints
 const encoding13 = {
   preencode(state, m) {
-    state.end++ // max flag is 1 so always one byte
+    state.end++ // max flag is 2 so always one byte
 
     if (m.contiguousLength) c.uint.preencode(state, m.contiguousLength)
+    if (m.remoteContiguousLength) c.uint.preencode(state, m.remoteContiguousLength)
   },
   encode(state, m) {
-    const flags = m.contiguousLength ? 1 : 0
+    const flags =
+      (m.contiguousLength ? 1 : 0) |
+      (m.remoteContiguousLength ? 2 : 0)
 
     c.uint.encode(state, flags)
 
     if (m.contiguousLength) c.uint.encode(state, m.contiguousLength)
+    if (m.remoteContiguousLength) c.uint.encode(state, m.remoteContiguousLength)
   },
   decode(state) {
     const flags = c.uint.decode(state)
 
     return {
-      contiguousLength: (flags & 1) !== 0 ? c.uint.decode(state) : 0
+      contiguousLength: (flags & 1) !== 0 ? c.uint.decode(state) : 0,
+      remoteContiguousLength: (flags & 2) !== 0 ? c.uint.decode(state) : 0
     }
   }
 }

spec/hyperschema/schema.json

@@ -348,6 +348,11 @@
           "name": "contiguousLength",
           "type": "uint",
           "version": 1
+        },
+        {
+          "name": "remoteContiguousLength",
+          "type": "uint",
+          "version": 1
         }
       ]
     },

test/atomic.js

@@ -186,7 +186,8 @@ test('atomized flow with all non-delete operations on a single core', async (t)
     length: 3
   }
   const expHints = {
-    contiguousLength: 1
+    contiguousLength: 1,
+    remoteContiguousLength: 0
   }
   const expBitfields = [b4a.from('bitfield-data-1'), null]
 

test/basic.js

@@ -242,7 +242,8 @@ test('can get info from store efficiently', async function (t) {
       },
       head: { fork: 0, length: 2, rootHash: b4a.alloc(32, 0), signature: null },
       hints: {
-        contiguousLength: 0
+        contiguousLength: 0,
+        remoteContiguousLength: 0
       }
     })
   }

test/core.js

@@ -399,7 +399,7 @@ test('set and get hypercore hints', async (t) => {
     const rx = core.read()
     const p = rx.getHints()
     rx.tryFlush()
-    t.alike(await p, { contiguousLength: 1 }, 'updated hints')
+    t.alike(await p, { contiguousLength: 1, remoteContiguousLength: 0 }, 'updated hints')
   }
 })