1 files changed, 77 insertions, 0 deletions
diff --git a/packages/sol-cov/src/source_maps.ts b/packages/sol-cov/src/source_maps.ts
new file mode 100644
index 000000000..795b15a9b
--- /dev/null
+++ b/packages/sol-cov/src/source_maps.ts
@@ -0,0 +1,77 @@
+import * as _ from 'lodash';
+
+import { getPcToInstructionIndexMapping } from './instructions';
+import { LineColumn, LocationByOffset, SourceRange } from './types';
+
+const RADIX = 10;
+
+export interface SourceLocation {
+    offset: number;
+    length: number;
+    fileIndex: number;
+}
+
+export const getLocationByOffset = (str: string) => {
+    const locationByOffset: LocationByOffset = {};
+    let currentOffset = 0;
+    for (const char of str.split('')) {
+        const location = locationByOffset[currentOffset - 1] || { line: 1, column: 0 };
+        const isNewline = char === '\n';
+        locationByOffset[currentOffset] = {
+            line: location.line + (isNewline ? 1 : 0),
+            column: isNewline ? 0 : location.column + 1,
+        };
+        currentOffset++;
+    }
+    return locationByOffset;
+};
+
+// Parses a sourcemap string
+// The solidity sourcemap format is documented here: https://github.com/ethereum/solidity/blob/develop/docs/miscellaneous.rst#source-mappings
+export const parseSourceMap = (sourceCodes: string[], srcMap: string, bytecodeHex: string, sources: string[]) => {
+    const bytecode = Uint8Array.from(Buffer.from(bytecodeHex, 'hex'));
+    const pcToInstructionIndex: { [programCounter: number]: number } = getPcToInstructionIndexMapping(bytecode);
+    const locationByOffsetByFileIndex = _.map(sourceCodes, getLocationByOffset);
+    const entries = srcMap.split(';');
+    const parsedEntries: SourceLocation[] = [];
+    let lastParsedEntry: SourceLocation = {} as any;
+    const instructionIndexToSourceRange: { [instructionIndex: number]: SourceRange } = {};
+    _.each(entries, (entry: string, i: number) => {
+        const [instructionIndexStrIfExists, lengthStrIfExists, fileIndexStrIfExists, jumpTypeStrIfExists] = entry.split(
+            ':',
+        );
+        const instructionIndexIfExists = parseInt(instructionIndexStrIfExists, RADIX);
+        const lengthIfExists = parseInt(lengthStrIfExists, RADIX);
+        const fileIndexIfExists = parseInt(fileIndexStrIfExists, RADIX);
+        const offset = _.isNaN(instructionIndexIfExists) ? lastParsedEntry.offset : instructionIndexIfExists;
+        const length = _.isNaN(lengthIfExists) ? lastParsedEntry.length : lengthIfExists;
+        const fileIndex = _.isNaN(fileIndexIfExists) ? lastParsedEntry.fileIndex : fileIndexIfExists;
+        const parsedEntry = {
+            offset,
+            length,
+            fileIndex,
+        };
+        if (parsedEntry.fileIndex !== -1) {
+            const sourceRange = {
+                location: {
+                    start: locationByOffsetByFileIndex[parsedEntry.fileIndex][parsedEntry.offset - 1],
+                    end:
+                        locationByOffsetByFileIndex[parsedEntry.fileIndex][parsedEntry.offset + parsedEntry.length - 1],
+                },
+                fileName: sources[parsedEntry.fileIndex],
+            };
+            instructionIndexToSourceRange[i] = sourceRange;
+        } else {
+            // Some assembly code generated by Solidity can't be mapped back to a line of source code.
+            // Source: https://github.com/ethereum/solidity/issues/3629
+        }
+        lastParsedEntry = parsedEntry;
+    });
+    const pcsToSourceRange: { [programCounter: number]: SourceRange } = {};
+    for (const programCounterKey of _.keys(pcToInstructionIndex)) {
+        const pc = parseInt(programCounterKey, RADIX);
+        const instructionIndex: number = pcToInstructionIndex[pc];
+        pcsToSourceRange[pc] = instructionIndexToSourceRange[instructionIndex];
+    }
+    return pcsToSourceRange;
+};