Refactor out common range parsing code in storages

We made a similar change in Miniflare 2 recently

Author: mrbbot

packages/tre/src/storage/file.ts

@@ -15,6 +15,7 @@ import {
   StoredKeyMeta,
   StoredMeta,
   StoredValueMeta,
+  parseRange,
 } from "./storage";
 
 export interface FileRange {
@@ -57,25 +58,7 @@ export async function readFileRange(
     filePath = await fs.realpath(filePath);
     const { size } = await fs.lstat(filePath);
     // build offset and length as necessary
-    if (suffix !== undefined) {
-      if (suffix <= 0) {
-        throw new Error("Suffix must be > 0");
-      }
-      if (suffix > size) suffix = size;
-      offset = size - suffix;
-      length = size - offset;
-    }
-    if (offset === undefined) offset = 0;
-    if (length === undefined) {
-      // get length of file
-      length = size - offset;
-    }
-
-    // check offset and length are valid
-    if (offset < 0) throw new Error("Offset must be >= 0");
-    if (offset >= size) throw new Error("Offset must be < size");
-    if (length <= 0) throw new Error("Length must be > 0");
-    if (offset + length > size) length = size - offset;
+    ({ offset, length } = parseRange({ offset, length, suffix }, size));
 
     // read file
     fd = await fs.open(filePath, "r");

packages/tre/src/storage/memory.ts

@@ -8,34 +8,9 @@ import {
   StoredMeta,
   StoredValueMeta,
   cloneMetadata,
+  parseRange,
 } from "./storage";
 
-export function parseRange(
-  { offset, length, suffix }: Range,
-  size: number
-): Required<Pick<Range, "offset" | "length">> {
-  // build proper offset and length
-  if (suffix !== undefined) {
-    if (suffix <= 0) {
-      throw new Error("Suffix must be > 0");
-    }
-    if (suffix > size) suffix = size;
-    offset = size - suffix;
-    length = size - offset;
-  }
-  if (offset === undefined) offset = 0;
-  if (length === undefined) length = size - offset;
-
-  // if offset is negative or greater than size, throw an error
-  if (offset < 0) throw new Error("Offset must be >= 0");
-  if (offset >= size) throw new Error("Offset must be < size");
-  // if length is less than or equal to 0, throw an error
-  if (length <= 0) throw new Error("Length must be > 0");
-  // if length goes beyond actual length, adjust length to the end of the value
-  if (offset + length > size) length = size - offset;
-
-  return { offset, length };
-}
 export class MemoryStorage extends LocalStorage {
   #sqliteDatabase?: DatabaseType;
 
@@ -87,7 +62,6 @@ export class MemoryStorage extends LocalStorage {
     if (stored === undefined) return;
     const { value } = stored;
     const size = value.byteLength;
-
     const { offset, length } = parseRange(range, size);
 
     return {

packages/tre/src/storage/sqlite.ts

@@ -2,14 +2,14 @@ import crypto from "crypto";
 import Database, { Database as DatabaseType } from "better-sqlite3";
 import { defaultClock } from "../shared";
 import { LocalStorage } from "./local";
-import { parseRange } from "./memory";
 import {
   Range,
   RangeStoredValueMeta,
   StoredKey,
   StoredKeyMeta,
   StoredMeta,
   StoredValueMeta,
+  parseRange,
 } from "./storage";
 
 // Don't use this!

packages/tre/src/storage/storage.ts

@@ -45,6 +45,35 @@ export interface Range {
   length?: number;
   suffix?: number;
 }
+export interface ParsedRange {
+  offset: number;
+  length: number;
+}
+export function parseRange(
+  { offset, length, suffix }: Range,
+  size: number
+): ParsedRange {
+  if (suffix !== undefined) {
+    if (suffix <= 0) {
+      throw new Error("Suffix must be > 0");
+    }
+    if (suffix > size) suffix = size;
+    offset = size - suffix;
+    length = size - offset;
+  }
+  if (offset === undefined) offset = 0;
+  if (length === undefined) length = size - offset;
+
+  // If offset is negative or greater than size, throw an error
+  if (offset < 0) throw new Error("Offset must be >= 0");
+  if (offset > size) throw new Error("Offset must be < size");
+  // If length is less than or equal to 0, throw an error
+  if (length <= 0) throw new Error("Length must be > 0");
+  // If length goes beyond actual length, adjust length to the end of the value
+  if (offset + length > size) length = size - offset;
+
+  return { offset, length };
+}
 
 export interface StorageListOptions {
   // Stage 1: filtering