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Fixes the size_hint implementation for BigIntAsHex parity scale codec encoding so that encoding 0 returns the correct size hint of 2 bytes (1 sign/len byte + 1 data byte) instead of 1 byte.
Type of change
Please check one:
Bug fix (fixes incorrect behavior)
New feature
Performance improvement
Documentation change with concrete technical impact
Style, wording, formatting, or typo-only change
Why is this change needed?
The size_hint method was computing the encoded size as 1 + bits.div_ceil(8), where bits is the number of bits in the value. For the value 0, bits() returns 0, so div_ceil(8) also returns 0, yielding a size hint of 1. However, the actual encode implementation always emits at least one data byte — 0 encodes as [sign_len_byte, 0x00], which is 2 bytes. This mismatch between size_hint and the actual encoded length is incorrect.
What was the behavior or documentation before?
size_hint for BigIntAsHex returned 1 when encoding 0, underreporting the actual encoded size by 1 byte.
What is the behavior or documentation after?
size_hint now returns at least 2 for any value (including 0), correctly reflecting that the encoder always emits a minimum of one data byte in addition to the sign/length byte.
Related issue or discussion (if any)
Additional context
The fix applies .max(1) to the div_ceil(8) result, ensuring the data byte count is never reported as zero.
Low Risk
Single-line sizing fix in codec hints only; no change to encode/decode logic or wire format.
Overview
Fixes BigIntAsHex parity-scale Encode::size_hint so it matches encode_to: the data length term now uses .max(1), because encoding always writes at least one payload byte (e.g. 0 → sign/len byte + 0x00, 2 bytes total).
Previously bits().div_ceil(8) was 0 for zero, so the hint was 1 byte while the encoder emitted 2.
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@eytan-starkware reviewed 1 file and all commit messages, and made 1 comment. Reviewable status: complete! all files reviewed, all discussions resolved (waiting on TomerStarkware).
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complete! all files reviewed, all discussions resolved (waiting on TomerStarkware).
Summary
Fixes the
size_hintimplementation forBigIntAsHexparity scale codec encoding so that encoding0returns the correct size hint of 2 bytes (1 sign/len byte + 1 data byte) instead of 1 byte.Type of change
Please check one:
Why is this change needed?
The
size_hintmethod was computing the encoded size as1 + bits.div_ceil(8), wherebitsis the number of bits in the value. For the value0,bits()returns0, sodiv_ceil(8)also returns0, yielding a size hint of1. However, the actualencodeimplementation always emits at least one data byte —0encodes as[sign_len_byte, 0x00], which is 2 bytes. This mismatch betweensize_hintand the actual encoded length is incorrect.What was the behavior or documentation before?
size_hintforBigIntAsHexreturned1when encoding0, underreporting the actual encoded size by 1 byte.What is the behavior or documentation after?
size_hintnow returns at least2for any value (including0), correctly reflecting that the encoder always emits a minimum of one data byte in addition to the sign/length byte.Related issue or discussion (if any)
Additional context
The fix applies
.max(1)to thediv_ceil(8)result, ensuring the data byte count is never reported as zero.