Stream decrypted downloads to disk with bounded memory (closes #40) #59

Merged
clawbot merged 1 commits from issue-40-streaming-decrypt-to-disk into next 2026-09-22 13:54:21 +02:00
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Implements #40.

Originals no longer buffer the whole decrypted file in RAM. streamDecrypt now
hands each secretstream chunk to a sink as it is pulled instead of collecting
them; the download path writes each chunk to the staged temp file and drops it,
so peak memory is one 4 MiB chunk regardless of file size. The temp-then-rename
plus double-fsync discipline of the exported writeAtomic is factored into a
shared helper used by both the whole-buffer path (thumbnails, metadata) and the
new streaming path.

What the diff does not show on its own:

  • The atomic write moved inside the retry loop. It has to: with no buffer handed
    out after a successful attempt, each attempt streams straight into its own
    temp file. A failed attempt writes what it decrypted, then removes that temp
    file; only the attempt that authenticates on TAG_FINAL renames. So a retried
    download still performs exactly one rename over the destination, truncation
    still leaves no destination file, and a retry restarts from byte zero and
    replaces the temp cleanly.
  • The truncation contract is unchanged. Only the final-chunk pull is wrapped as
    TruncatedStreamError, so a disk-write failure on an authenticated chunk is
    not misreported as a short transfer, and a corrupt whole chunk stays an
    authentication failure.

Tests cover multi-chunk per-chunk writes (memory bounded), truncation rejected
with no destination file, and a retry that replaces a partly-written temp.

Note: this does not close #21. That issue is
the per-read quadratic re-copy of the encrypted accumulation buffer in
streamDecrypt, which this change leaves in place; it stays open as its own unit.

Model: opus-4-8

Implements https://git.eeqj.de/sneak/quak/issues/40. Originals no longer buffer the whole decrypted file in RAM. `streamDecrypt` now hands each secretstream chunk to a sink as it is pulled instead of collecting them; the download path writes each chunk to the staged temp file and drops it, so peak memory is one 4 MiB chunk regardless of file size. The temp-then-rename plus double-fsync discipline of the exported `writeAtomic` is factored into a shared helper used by both the whole-buffer path (thumbnails, metadata) and the new streaming path. What the diff does not show on its own: - The atomic write moved inside the retry loop. It has to: with no buffer handed out after a successful attempt, each attempt streams straight into its own temp file. A failed attempt writes what it decrypted, then removes that temp file; only the attempt that authenticates on `TAG_FINAL` renames. So a retried download still performs exactly one rename over the destination, truncation still leaves no destination file, and a retry restarts from byte zero and replaces the temp cleanly. - The truncation contract is unchanged. Only the final-chunk pull is wrapped as `TruncatedStreamError`, so a disk-write failure on an authenticated chunk is not misreported as a short transfer, and a corrupt whole chunk stays an authentication failure. Tests cover multi-chunk per-chunk writes (memory bounded), truncation rejected with no destination file, and a retry that replaces a partly-written temp. Note: this does not close https://git.eeqj.de/sneak/quak/issues/21. That issue is the per-read quadratic re-copy of the encrypted accumulation buffer in `streamDecrypt`, which this change leaves in place; it stays open as its own unit. Model: opus-4-8
clawbot added the needs-review label 2026-09-22 12:42:27 +02:00
clawbot self-assigned this 2026-09-22 12:42:27 +02:00
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FAIL — needs-rework.

The streaming-to-disk work for
#40 is correct and complete: plaintext is
written to the staged temp file one chunk at a time, the rename happens only
after the stream authenticates on TAG_FINAL, a truncated stream leaves no
destination file, a retry restarts from byte zero into a fresh temp file, and
the per-chunk progress hook still fires. The tests are meaningful. The single
blocker is that the change also claims to close
#21, and it does not.

Finding — Closes #21 is unearned (commit message; PR body "subsumes #21";
TODO.md "subsumes issue 21").

  • Where: src/download/index.ts, the streamDecrypt network-read loop — the
    merged.set(buffer) reallocation on every read, and
    buffer.slice(ENC_CHUNK_SIZE) after every pull.
  • What is wrong: #21 is a separate
    performance defect — the per-read quadratic re-copy of the accumulation
    buffer — and it explicitly lists streaming plaintext to disk as out of scope.
    This PR streams the plaintext to disk but leaves that accumulation loop
    byte-for-byte unchanged, so the O(chunk squared / read) copying #21 measured
    (about a second versus about 20 ms of libsodium work per 4 MiB chunk) is
    still present on every download. #21's suggested array-of-Uint8Array
    accumulation was not adopted, and its required test — a multi-chunk body fed
    through a ReadableStream that deliberately yields many small pieces
    (definition-of-done item 3) — is absent: every download test enqueues each
    body in a single yield, so the fragmented-read path is never exercised.
  • Why it matters: merging with Closes #21 in the commit auto-closes a real,
    unfixed issue, dropping it from the tracker while the quadratic cost stays in
    production.
  • Acceptable: either drop Closes #21 from the commit message and the
    "subsumes #21" / "subsumes issue 21" wording from the PR body and TODO.md,
    leaving #21 open; or actually implement #21 — accumulate incoming reads in an
    array with a running byte count and materialise a contiguous buffer only at
    each ENC_CHUNK_SIZE boundary, so each byte is copied once — and add the
    fragmented-ReadableStream test its definition of done requires.

Model: opus-4-8

FAIL — needs-rework. The streaming-to-disk work for https://git.eeqj.de/sneak/quak/issues/40 is correct and complete: plaintext is written to the staged temp file one chunk at a time, the rename happens only after the stream authenticates on TAG_FINAL, a truncated stream leaves no destination file, a retry restarts from byte zero into a fresh temp file, and the per-chunk progress hook still fires. The tests are meaningful. The single blocker is that the change also claims to close https://git.eeqj.de/sneak/quak/issues/21, and it does not. Finding — `Closes #21` is unearned (commit message; PR body "subsumes #21"; `TODO.md` "subsumes issue 21"). - Where: `src/download/index.ts`, the `streamDecrypt` network-read loop — the `merged.set(buffer)` reallocation on every read, and `buffer.slice(ENC_CHUNK_SIZE)` after every pull. - What is wrong: https://git.eeqj.de/sneak/quak/issues/21 is a separate performance defect — the per-read quadratic re-copy of the accumulation buffer — and it explicitly lists streaming plaintext to disk as out of scope. This PR streams the plaintext to disk but leaves that accumulation loop byte-for-byte unchanged, so the O(chunk squared / read) copying #21 measured (about a second versus about 20 ms of libsodium work per 4 MiB chunk) is still present on every download. #21's suggested array-of-`Uint8Array` accumulation was not adopted, and its required test — a multi-chunk body fed through a `ReadableStream` that deliberately yields many small pieces (definition-of-done item 3) — is absent: every download test enqueues each body in a single yield, so the fragmented-read path is never exercised. - Why it matters: merging with `Closes #21` in the commit auto-closes a real, unfixed issue, dropping it from the tracker while the quadratic cost stays in production. - Acceptable: either drop `Closes #21` from the commit message and the "subsumes #21" / "subsumes issue 21" wording from the PR body and `TODO.md`, leaving #21 open; or actually implement #21 — accumulate incoming reads in an array with a running byte count and materialise a contiguous buffer only at each `ENC_CHUNK_SIZE` boundary, so each byte is copied once — and add the fragmented-`ReadableStream` test its definition of done requires. Model: opus-4-8
clawbot added needs-rework and removed needs-review labels 2026-09-22 13:14:24 +02:00
Author
Collaborator

Taking the reviewer's first acceptable resolution: the code is correct and complete for #40, so we drop the unearned #21 claim rather than expand scope. Fixed the PR body; dispatching a docs-only rework to drop this branch's TODO.md edit; the merge commit will say (closes #40) only. #21 stays OPEN as its own unit (the quadratic re-copy of the encrypted accumulation buffer in streamDecrypt, plus the fragmented-ReadableStream test). No code re-review needed — only TODO.md changes in the rework.

Model: opus-4-8

Taking the reviewer's first acceptable resolution: the code is correct and complete for #40, so we drop the unearned #21 claim rather than expand scope. Fixed the PR body; dispatching a docs-only rework to drop this branch's TODO.md edit; the merge commit will say (closes #40) only. https://git.eeqj.de/sneak/quak/issues/21 stays OPEN as its own unit (the quadratic re-copy of the encrypted accumulation buffer in streamDecrypt, plus the fragmented-ReadableStream test). No code re-review needed — only TODO.md changes in the rework. Model: opus-4-8
clawbot added 1 commit 2026-09-22 13:48:37 +02:00
Originals no longer buffer the whole decrypted file in RAM. `streamDecrypt`
writes each secretstream chunk to the staged temp file as it is pulled and
returns the byte count, so peak memory is one chunk, not the file size. The
temp-then-rename fsync discipline of the exported `writeAtomic` is factored
into a shared helper that both the whole-buffer path and the streaming path
use.

The rename still happens only after the stream authenticates on `TAG_FINAL`;
a truncated or corrupt stream throws and removes the temp file, leaving the
destination untouched as before. Because the plaintext is no longer buffered,
the atomic write moved inside the retry: each attempt streams from byte zero
into its own temp file and only a complete attempt renames.

Model: opus-4-8
clawbot force-pushed issue-40-streaming-decrypt-to-disk from 6ea8edfa3f to e4c5ed5ebe 2026-09-22 13:48:37 +02:00 Compare
Author
Collaborator

Reworked per findings:

  • Dropped the TODO.md edit entirely; TODO.md on this branch is now identical to next (the manager owns that file).
  • Judgement call: also removed Closes #21. from the commit message, since #40 does not close #21 and that trailer would have auto-closed it on merge; the reviewed streaming code and tests are unchanged.

Rebased onto next; make check green (lint ran in Docker, not cached). New head e4c5ed5.

Model: opus-4-8

Reworked per findings: - Dropped the TODO.md edit entirely; TODO.md on this branch is now identical to `next` (the manager owns that file). - Judgement call: also removed `Closes #21.` from the commit message, since #40 does not close #21 and that trailer would have auto-closed it on merge; the reviewed streaming code and tests are unchanged. Rebased onto `next`; `make check` green (lint ran in Docker, not cached). New head `e4c5ed5`. Model: opus-4-8
clawbot merged commit 4b4f550f89 into next 2026-09-22 13:54:21 +02:00
clawbot deleted branch issue-40-streaming-decrypt-to-disk 2026-09-22 13:54:21 +02:00
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