decompress .json.zstd fetched by getSaveData

src/config/AppConfig.ts

@@ -10,11 +10,11 @@ export const defaultConfig = {
         // Size of a save if it is uploaded as uncompressed. The browser packs
         // saves as a stream, so these limits are about the backend's disk
         // rather than about memory.
-        maxSizePlainTextBytes: 200 * 1024 * 1024,
+        maxSizePlainTextMB: 200,
         // Archives produced by the game, recognized by the zip magic bytes.
-        maxSizeCompressedBytes: 60 * 1024 * 1024,
+        maxSizeCompressedMB: 60,
         // read COMPRESSION.md
-        zstdCompressionLevel: 11,
+        zstdCompressionLevel: 10,
     },
 }
 

src/lib/formatBytes.ts

@@ -1,5 +1,5 @@
-const KILOBYTE = 1024
-const MEGABYTE = 1024 * KILOBYTE
+export const KILOBYTE = 1024
+export const MEGABYTE = 1024 * KILOBYTE
 
 /**
  * Formats a byte count for error messages and status lines, e.g. "12.3 MB".

src/lib/saveArchive/client.ts

@@ -3,7 +3,7 @@
 
 import type { SaveUploadConfig } from '@/config/AppConfig'
 import { GAME_SAVE_ENTRY_NAMES, GameEnum } from '@/config/games'
-import { formatBytes } from '@/lib/formatBytes'
+import { formatBytes, MEGABYTE } from '@/lib/formatBytes'
 import { isZipFile } from './gameZip'
 import {
     OriginalFileType,
@@ -68,9 +68,10 @@ export async function packSaveForUpload(
     onStage: StageCallback
 ): Promise<PackedSave> {
     const isZip = await isZipFile(file)
-    const sizeLimit = isZip
-        ? config.maxSizeCompressedBytes
-        : config.maxSizePlainTextBytes
+    // The limits are configured in megabytes, file sizes are in bytes.
+    const sizeLimit =
+        (isZip ? config.maxSizeCompressedMB : config.maxSizePlainTextMB) *
+        MEGABYTE
 
     if (file.size > sizeLimit) {
         const saveKind = isZip ? 'archived' : 'plain text'

src/services/SaveParserBackendService.ts

@@ -3,6 +3,7 @@ import type { SaveUploadConfig } from '@/config/AppConfig'
 import { GameEnum } from '@/config/games'
 import { packSaveForUpload, StageCallback } from '@/lib/saveArchive/client'
 import { OriginalFileType } from '@/lib/saveArchive/messages'
+import { createZstdDecompressStream } from '@/lib/saveArchive/zstdStream'
 
 export interface UploadSaveResponse {
     id: string
@@ -86,7 +87,12 @@ export class SaveParserBackendService {
         return await response.json()
     }
 
-    // Fetches the fully parsed data for a save once its parsing is done.
+    /**
+     * Fetches the fully parsed data for a save once its parsing is done.
+     *
+     * The backend stores and serves that data as zstd compressed json, so the
+     * body is decompressed on the way in rather than read as text first.
+     */
     async getSaveData(id: string): Promise<Record<string, unknown>> {
         const url = `${this.API_BASE}/getSaveData?id=${encodeURIComponent(id)}`
         const response = await fetch(url)
@@ -97,8 +103,16 @@ export class SaveParserBackendService {
                     (await getBodyTextOrEmpty(response))
             )
         }
+        // A body is only missing on a response that cannot carry one, which a
+        // successful getSaveData never is.
+        if (!response.body) {
+            throw new Error('Failed to get parsed save: response has no body')
+        }
 
-        return await response.json()
+        // Decompresses as the bytes arrive, so the compressed json is never
+        // held whole; only the parsed object stays in memory.
+        const json = response.body.pipeThrough(createZstdDecompressStream())
+        return await new Response(json).json()
     }
 
     /**