fix: byte-range request body size

packages/verified-fetch/src/utils/byte-range-context.ts

@@ -117,12 +117,35 @@
     return body
   }
 
-  // TODO: we should be able to use this.offset and this.length to slice the body
   private getSlicedBody <T extends SliceableBody>(body: T): SliceableBody {
     const offset = this.byteStart ?? 0
-    const length = this.byteEnd == null ? undefined : this.byteEnd + 1
-    this.log.trace('returning body with offset %o and length %o', offset, length)
-    return body.slice(offset, length) satisfies SliceableBody
+
+    // Calculate the correct number of bytes to return
+    // For a range like bytes=1000-2000, we want exactly 1001 bytes
+    let length: number | undefined
+
+    if (this.byteEnd != null && this.byteStart != null) {
+      // Exact number of bytes is (end - start + 1) due to inclusive ranges
+      length = this.byteEnd - this.byteStart + 1
+    } else {
+      length = undefined
+    }
+
+    this.log.trace('slicing body with offset=%o and length=%o', offset, length)
+
+    if (typeof body === 'string') {
+      // String slicing works with start and end indices
+      return body.slice(offset, length !== undefined ? offset + length : undefined) satisfies SliceableBody
+    } else if (body instanceof Blob) {
+      // Blob.slice takes start and end positions
+      return body.slice(offset, length !== undefined ? offset + length : undefined) satisfies SliceableBody
+    } else if (body instanceof ArrayBuffer || body instanceof Uint8Array) {
+      // ArrayBuffer.slice and Uint8Array.slice take start and end positions
+      return body.slice(offset, length !== undefined ? offset + length : undefined) satisfies SliceableBody
+    } else {
+      // This should never happen due to type constraints
+      return body as SliceableBody
+    }
   }
 
   /**
@@ -228,14 +251,15 @@
    * 2. slicing the body
    */
   public get length (): number | undefined {
-    if (this.byteEnd != null && this.byteStart != null && this.byteStart === this.byteEnd) {
-      return 1
+    if (this.byteEnd != null && this.byteStart != null) {
+      // For a range like bytes=1000-2000, we want a length of 1001 bytes
+      return this.byteEnd - this.byteStart + 1
     }
     if (this.byteEnd != null) {
       return this.byteEnd + 1
     }
 
-    return this.byteSize != null ? this.byteSize - 1 : undefined
+    return this.byteSize
   }
 
   /**

packages/verified-fetch/test/utils/byte-range-context.spec.ts

@@ -43,6 +43,7 @@ describe('ByteRangeContext', () => {
   })
 
   const array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
+  const largeArray = Array.from({ length: 3000 }, (_, i) => i + 1)
   const uint8arrayRangeTests = [
     // full ranges:
     { type: 'Uint8Array', range: 'bytes=0-10', contentRange: 'bytes 0-10/11', body: new Uint8Array(array), expected: new Uint8Array(array) },
@@ -63,12 +64,14 @@ describe('ByteRangeContext', () => {
     { type: 'Uint8Array', range: 'bytes=1-', contentRange: 'bytes 1-10/11', body: new Uint8Array(array), expected: new Uint8Array([2, 3, 4, 5, 6, 7, 8, 9, 10, 11]) },
     { type: 'Uint8Array', range: 'bytes=2-', contentRange: 'bytes 2-10/11', body: new Uint8Array(array), expected: new Uint8Array([3, 4, 5, 6, 7, 8, 9, 10, 11]) },
     { type: 'Uint8Array', range: 'bytes=-2', contentRange: 'bytes 9-10/11', body: new Uint8Array(array), expected: new Uint8Array(array.slice(-2)) },
+    { type: 'Uint8Array', range: 'bytes=1000-2000', contentRange: 'bytes 1000-2000/3000', body: new Uint8Array(largeArray), expected: new Uint8Array(largeArray.slice(1000, 2001)) }, // https://github.com/ipfs/helia-verified-fetch/issues/184
 
     // single byte ranges:
     { type: 'Uint8Array', range: 'bytes=1-1', contentRange: 'bytes 1-1/11', body: new Uint8Array(array), expected: new Uint8Array(array.slice(1, 2)) },
     { type: 'Uint8Array', range: 'bytes=-1', contentRange: 'bytes 10-10/11', body: new Uint8Array(array), expected: new Uint8Array(array.slice(-1)) }
 
   ]
+
   const validRanges = [
     ...uint8arrayRangeTests,
     ...uint8arrayRangeTests.map(({ range, contentRange, body, expected }) => ({