Implement Map type (#61)

* Implement Map type

* add test

* readme note

README.md

@@ -173,7 +173,7 @@ Most of the unsupported types should be pretty straightforward to implement; the
 - [x] Large List (Not implemented by Arrow JS but supported by downcasting to `List`.)
 - [x] Fixed-size List
 - [x] Struct
-- [ ] Map
+- [x] Map (though not yet tested, see [#97](https://github.com/kylebarron/arrow-js-ffi/issues/97))
 - [x] Dense Union
 - [x] Sparse Union
 - [x] Dictionary-encoded arrays

src/field.ts

@@ -222,6 +222,13 @@ function parseFieldContent({
     return new arrow.Field(name, type, flags.nullable, metadata);
   }
 
+  // Map
+  if (formatString === "+m") {
+    assert(childrenFields.length === 1);
+    const type = new arrow.Map_(childrenFields[0], flags.mapKeysSorted);
+    return new arrow.Field(name, type, flags.nullable, metadata);
+  }
+
   // Dense union
   if (formatString.slice(0, 4) === "+ud:") {
     const typeIds = formatString.slice(4).split(",").map(Number);

src/vector.ts

@@ -669,6 +669,36 @@ function parseDataContent<T extends DataType>({
     });
   }
 
+  if (DataType.isMap(dataType)) {
+    assert(nChildren === 1);
+    const [validityPtr, offsetsPtr] = bufferPtrs;
+    const nullBitmap = parseNullBitmap(
+      dataView.buffer,
+      validityPtr,
+      length,
+      copy,
+    );
+    const valueOffsets = copy
+      ? new Int32Array(
+          copyBuffer(
+            dataView.buffer,
+            offsetsPtr,
+            (length + 1) * Int32Array.BYTES_PER_ELEMENT,
+          ),
+        )
+      : new Int32Array(dataView.buffer, offsetsPtr, length + 1);
+
+    return arrow.makeData({
+      type: dataType,
+      offset,
+      length,
+      nullCount,
+      nullBitmap,
+      valueOffsets,
+      child: children[0],
+    });
+  }
+
   if (DataType.isDenseUnion(dataType)) {
     const [typeIdsPtr, offsetsPtr] = bufferPtrs;
 

tests/ffi.test.ts

@@ -683,6 +683,45 @@ describe("nullable int", (t) => {
   it("copy=true", () => test(true));
 });
 
+// Skipping this test because of rust issues
+// ref: https://github.com/kylebarron/arrow-js-ffi/issues/97
+describe.skip("map array", (t) => {
+  function test(copy: boolean) {
+    let columnIndex = TEST_TABLE.schema.fields.findIndex(
+      (field) => field.name == "map_array"
+    );
+
+    const originalField = TEST_TABLE.schema.fields[columnIndex];
+    // declare it's not null
+    const originalVector = TEST_TABLE.getChildAt(columnIndex) as arrow.Vector;
+    const fieldPtr = FFI_TABLE.schemaAddr(columnIndex);
+    const field = parseField(WASM_MEMORY.buffer, fieldPtr);
+
+    expect(field.name).toStrictEqual(originalField.name);
+    expect(field.typeId).toStrictEqual(originalField.typeId);
+    expect(field.nullable).toStrictEqual(originalField.nullable);
+
+    const arrayPtr = FFI_TABLE.arrayAddr(0, columnIndex);
+    const wasmVector = parseVector(
+      WASM_MEMORY.buffer,
+      arrayPtr,
+      field.type,
+      copy
+    );
+
+    console.log(originalVector);
+    console.log(wasmVector);
+
+    // expect(
+    //   validityEqual(originalVector, wasmVector),
+    //   "validity should be equal"
+    // ).toBeTruthy();
+  }
+
+  it("copy=false", () => test(false));
+  it("copy=true", () => test(true));
+});
+
 describe("dictionary encoded string", (t) => {
   function test(copy: boolean) {
     let columnIndex = TEST_TABLE.schema.fields.findIndex(

tests/pyarrow_generate_data.py

@@ -140,6 +140,15 @@ def nullable_int() -> pa.Array:
     return arr
 
 
+def map_array() -> pa.Array:
+    offsets = [0, 2, 3, 4]
+    keys = ["a", "b", "a", "b"]
+    items = [1, 2, 3, 4]
+    arr = pa.MapArray.from_arrays(offsets, keys, items)
+    assert isinstance(arr, pa.MapArray)
+    return arr
+
+
 def sparse_union_array() -> pa.Array:
     """Generate a sparse union array
 
@@ -251,6 +260,9 @@ def table() -> pa.Table:
             "date64": date64_array(),
             "timestamp": timestamp_array(),
             "nullable_int": nullable_int(),
+            # We don't yet include "map" in tests because of issues on the Rust side.
+            # ref: https://github.com/kylebarron/arrow-js-ffi/issues/97
+            # "map": map_array(),
             "sparse_union": sparse_union_array(),
             "dense_union": dense_union_array(),
             "duration": duration_array(),

yarn.lock

@@ -338,10 +338,10 @@ __metadata:
   linkType: hard
 
 "@rollup/plugin-typescript@npm:^11.1.2":
-  version: 11.1.6
-  resolution: "@rollup/plugin-typescript@npm:11.1.6"
+  version: 11.1.5
+  resolution: "@rollup/plugin-typescript@npm:11.1.5"
   dependencies:
-    "@rollup/pluginutils": "npm:^5.1.0"
+    "@rollup/pluginutils": "npm:^5.0.1"
     resolve: "npm:^1.22.1"
   peerDependencies:
     rollup: ^2.14.0||^3.0.0||^4.0.0
@@ -352,23 +352,23 @@ __metadata:
       optional: true
     tslib:
       optional: true
-  checksum: 4ae4d6cfc929393171288df2f18b5eb837fa53d8689118d9661b3064567341f6f6cf8389af55f1d5f015e3682abf30a64ab609fdf75ecb5a84224505e407eb69
+  checksum: 3048c7837bcaae3770e6977aa22b34b7da3862f14f25a22249c83867be1a3f78138c0a62b28efd22037890dfd6933e960007da6667a945dcef45f585a581f1aa
   languageName: node
   linkType: hard
 
-"@rollup/pluginutils@npm:^5.1.0":
-  version: 5.1.0
-  resolution: "@rollup/pluginutils@npm:5.1.0"
+"@rollup/pluginutils@npm:^5.0.1":
+  version: 5.0.2
+  resolution: "@rollup/pluginutils@npm:5.0.2"
   dependencies:
     "@types/estree": "npm:^1.0.0"
     estree-walker: "npm:^2.0.2"
     picomatch: "npm:^2.3.1"
   peerDependencies:
-    rollup: ^1.20.0||^2.0.0||^3.0.0||^4.0.0
+    rollup: ^1.20.0||^2.0.0||^3.0.0
   peerDependenciesMeta:
     rollup:
       optional: true
-  checksum: abb15eaec5b36f159ec351b48578401bedcefdfa371d24a914cfdbb1e27d0ebfbf895299ec18ccc343d247e71f2502cba21202bc1362d7ef27d5ded699e5c2b2
+  checksum: 7aebf04d5d25d7d2e9514cc8f81a49b11f093b29eae2862da29022532b66e3de4681f537cc785fdcf438bcdefa3af4453470e7951ca91d6ebea2f41d6aea42d3
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@@ -2597,8 +2597,8 @@ __metadata:
   linkType: hard
 
 "ts-node@npm:^10.9.1":
-  version: 10.9.2
-  resolution: "ts-node@npm:10.9.2"
+  version: 10.9.1
+  resolution: "ts-node@npm:10.9.1"
   dependencies:
     "@cspotcode/source-map-support": "npm:^0.8.0"
     "@tsconfig/node10": "npm:^1.0.7"
@@ -2630,7 +2630,7 @@ __metadata:
     ts-node-script: dist/bin-script.js
     ts-node-transpile-only: dist/bin-transpile.js
     ts-script: dist/bin-script-deprecated.js
-  checksum: a91a15b3c9f76ac462f006fa88b6bfa528130dcfb849dd7ef7f9d640832ab681e235b8a2bc58ecde42f72851cc1d5d4e22c901b0c11aa51001ea1d395074b794
+  checksum: bee56d4dc96ccbafc99dfab7b73fbabc62abab2562af53cdea91c874a301b9d11e42bc33c0a032a6ed6d813dbdc9295ec73dde7b73ea4ebde02b0e22006f7e04
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@@ -2649,22 +2649,22 @@ __metadata:
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-  version: 5.3.3
-  resolution: "typescript@npm:5.3.3"
+  version: 5.2.2
+  resolution: "typescript@npm:5.2.2"
   bin:
     tsc: bin/tsc
     tsserver: bin/tsserver
-  checksum: 6e4e6a14a50c222b3d14d4ea2f729e79f972fa536ac1522b91202a9a65af3605c2928c4a790a4a50aa13694d461c479ba92cedaeb1e7b190aadaa4e4b96b8e18
+  checksum: d65e50eb849bd21ff8677e5b9447f9c6e74777e346afd67754934264dcbf4bd59e7d2473f6062d9a015d66bd573311166357e3eb07fea0b52859cf9bb2b58555
   languageName: node
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 "typescript@patch:typescript@npm%3A^5.2.2#optional!builtin<compat/typescript>":
-  version: 5.3.3
-  resolution: "typescript@patch:typescript@npm%3A5.3.3#optional!builtin<compat/typescript>::version=5.3.3&hash=e012d7"
+  version: 5.2.2
+  resolution: "typescript@patch:typescript@npm%3A5.2.2#optional!builtin<compat/typescript>::version=5.2.2&hash=f3b441"
   bin:
     tsc: bin/tsc
     tsserver: bin/tsserver
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