feat: backport index iter from ethutils

index_iter.go

@@ -0,0 +1,66 @@
+package celoutils
+
+import (
+	"context"
+	"math/big"
+
+	"github.com/celo-org/celo-blockchain/common"
+	"github.com/grassrootseconomics/w3-celo/module/eth"
+	"github.com/grassrootseconomics/w3-celo/w3types"
+)
+
+type BatchIterator struct {
+	provider     *Provider
+	index        common.Address
+	entryCount   *big.Int
+	currentIndex int64
+	batchSize    int64
+}
+
+const defaultBatchSize = 500
+
+func (p *Provider) NewBatchIterator(ctx context.Context, index common.Address) (*BatchIterator, error) {
+	var entryCount big.Int
+
+	if err := p.Client.CallCtx(
+		ctx,
+		eth.CallFunc(index, entryCountFunc).Returns(&entryCount),
+	); err != nil {
+		return nil, err
+	}
+
+	return &BatchIterator{
+		provider:     p,
+		index:        index,
+		entryCount:   &entryCount,
+		currentIndex: 0,
+		batchSize:    defaultBatchSize,
+	}, nil
+}
+
+func (iter *BatchIterator) Next(ctx context.Context) ([]common.Address, error) {
+	if iter.currentIndex >= iter.entryCount.Int64() {
+		return nil, nil
+	}
+
+	endIndex := iter.currentIndex + iter.batchSize
+	if endIndex > iter.entryCount.Int64() {
+		endIndex = iter.entryCount.Int64()
+	}
+
+	batchSize := endIndex - iter.currentIndex
+	calls := make([]w3types.RPCCaller, batchSize)
+	tokenAddresses := make([]common.Address, batchSize)
+
+	for i := int64(0); i < batchSize; i++ {
+		index := iter.currentIndex + i
+		calls[i] = eth.CallFunc(iter.index, entrySig, new(big.Int).SetInt64(index)).Returns(&tokenAddresses[i])
+	}
+
+	if err := iter.provider.Client.CallCtx(ctx, calls...); err != nil {
+		return nil, err
+	}
+
+	iter.currentIndex = endIndex
+	return tokenAddresses, nil
+}