1 files changed, 47 insertions, 0 deletions
diff --git a/packages/utils/src/abi_encoder/evm_data_types/string.ts b/packages/utils/src/abi_encoder/evm_data_types/string.ts
new file mode 100644
index 000000000..96b36e735
--- /dev/null
+++ b/packages/utils/src/abi_encoder/evm_data_types/string.ts
@@ -0,0 +1,47 @@
+/* tslint:disable prefer-function-over-method */
+import { DataItem } from 'ethereum-types';
+import * as ethUtil from 'ethereumjs-util';
+import * as _ from 'lodash';
+
+import { RawCalldata } from '../calldata';
+import * as Constants from '../constants';
+import { DataTypeFactory, PayloadDataType } from '../data_type';
+
+export class String extends PayloadDataType {
+    private static readonly _SIZE_KNOWN_AT_COMPILE_TIME: boolean = false;
+
+    public static matchType(type: string): boolean {
+        return type === 'string';
+    }
+
+    public constructor(dataItem: DataItem, dataTypeFactory: DataTypeFactory) {
+        super(dataItem, dataTypeFactory, String._SIZE_KNOWN_AT_COMPILE_TIME);
+        if (!String.matchType(dataItem.type)) {
+            throw new Error(`Tried to instantiate String with bad input: ${dataItem}`);
+        }
+    }
+
+    public encodeValue(value: string): Buffer {
+        const wordsForValue = Math.ceil(value.length / Constants.EVM_WORD_WIDTH_IN_BYTES);
+        const paddedDynamicBytesForValue = wordsForValue * Constants.EVM_WORD_WIDTH_IN_BYTES;
+        const valueBuf = ethUtil.setLengthRight(new Buffer(value), paddedDynamicBytesForValue);
+        const lengthBuf = ethUtil.setLengthLeft(ethUtil.toBuffer(value.length), Constants.EVM_WORD_WIDTH_IN_BYTES);
+        const encodedValueBuf = Buffer.concat([lengthBuf, valueBuf]);
+        return encodedValueBuf;
+    }
+
+    public decodeValue(calldata: RawCalldata): string {
+        const lengthBuf = calldata.popWord();
+        const lengthHex = ethUtil.bufferToHex(lengthBuf);
+        const length = parseInt(lengthHex, Constants.HEX_BASE);
+        const wordsForValue = Math.ceil(length / Constants.EVM_WORD_WIDTH_IN_BYTES);
+        const paddedValueBuf = calldata.popWords(wordsForValue);
+        const valueBuf = paddedValueBuf.slice(0, length);
+        const value = valueBuf.toString('ascii');
+        return value;
+    }
+
+    public getSignature(): string {
+        return 'string';
+    }
+}