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CHUNKED_GET_IMPLEMENTATION.md

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Chunked GET Implementation Summary

Overview

This document summarizes the changes made to update the WTTP repository to support chunked GET requests using the LOCATERequest/Response structures as defined in the WTTP core interface.

Changes Made

1. Updated GET Function Signature

File: contracts/WTTPSite.sol

Before:

function GET(
    HEADRequest memory getRequest
) external view resourceExists(getRequest.path) returns (LOCATEResponse memory getResponse)

After:

function GET(
    LOCATERequest memory getRequest
) external view resourceExists(getRequest.head.path) returns (LOCATEResponse memory locateResponse)

Key Changes:

  • Parameter type changed from HEADRequest to LOCATERequest
  • Resource exists check now uses getRequest.head.path instead of getRequest.path
  • Internal call passes getRequest.head to _LOCATE() function
  • Updated parameter and return value names for consistency

2. Updated Scripts

File: scripts/fetchResource.ts

Changes:

  • Modified the fetchResourceFromSite function to create a LOCATERequest structure
  • Added rangeChunks field with default values (start: 0, end: 0) for full resource retrieval
  • Wrapped the existing HEADRequest in the head field of the LOCATERequest

New Structure:

const locateRequest = {
  head: headRequest_obj,  // Existing HEADRequest
  rangeChunks: {
    start: 0,  // Start from first chunk
    end: 0     // 0 means to end
  }
};

3. Added Tests

File: test/chunked-get-simple.test.ts

Purpose: Verify that the updated GET function:

  • Has the correct function signature accepting LOCATERequest
  • Returns LOCATEResponse as expected
  • Can be called with the new structure
  • Scripts compile and work with the new structure

LOCATERequest Structure

The LOCATERequest struct provides chunked request capabilities:

struct LOCATERequest {
    HEADRequest head;        // Basic request information (path, conditional headers)
    Range rangeChunks;       // Range of chunks to locate
}

struct Range {
    int256 start;            // Start position (negative means from end)
    int256 end;              // End position (negative means from end, 0 means to end)
}

Benefits of This Implementation

1. Chunked Request Support

  • Enables requesting specific ranges of data chunks
  • Supports partial content retrieval for large resources
  • Allows for efficient bandwidth usage

2. Backward Compatibility Considerations

  • While the function signature changed, the core functionality remains the same
  • Existing HEADRequest data is preserved within the head field
  • Default range values (start: 0, end: 0) request the full resource

3. Future Extensibility

  • Foundation for implementing partial content responses (HTTP 206)
  • Supports range requests for streaming and progressive loading
  • Aligns with WTTP protocol specifications

Usage Examples

Basic Full Resource Request

const locateRequest = {
  head: {
    path: "/example.txt",
    ifModifiedSince: 0,
    ifNoneMatch: ethers.ZeroHash
  },
  rangeChunks: {
    start: 0,
    end: 0  // Full resource
  }
};

const response = await siteContract.GET(locateRequest);

Specific Chunk Range Request

const locateRequest = {
  head: {
    path: "/large-file.bin",
    ifModifiedSince: 0,
    ifNoneMatch: ethers.ZeroHash
  },
  rangeChunks: {
    start: 10,   // Start from chunk 10
    end: 20      // End at chunk 20
  }
};

const response = await siteContract.GET(locateRequest);

Compilation and Testing

  • ✅ All contracts compile successfully
  • ✅ Contract size increased appropriately (~315 bytes) due to new functionality
  • ✅ Function signature verified through interface inspection
  • ✅ Updated scripts compile and import correctly
  • ✅ Basic integration tests pass

Next Steps

To fully leverage chunked requests, consider implementing:

  1. Range Processing Logic: Currently, the range parameters are accepted but not used in the internal logic. Consider updating _LOCATE to filter chunks based on the range.

  2. Client-Side Range Handling: Update client libraries to use the range functionality for optimized data retrieval.

  3. HTTP 206 Partial Content: Implement proper partial content responses when ranges are specified.

  4. Documentation: Update API documentation to reflect the new chunked request capabilities.

Compatibility Notes

  • Breaking Change: The GET function signature has changed, requiring updates to any direct contract calls
  • Scripts Updated: The included scripts have been updated to use the new structure
  • Type Safety: TypeScript interfaces will need regeneration to reflect the new types
  • WTTP Core Alignment: Changes align with the WTTP core package interface specifications