Use constant size generic parameter for random bytes generation #2910
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All uses of `get_random()` were in the form of: `&get_random(vec![0u8; SIZE])` with `SIZE` being a constant. Building a `Vec` is unnecessary for two reasons. First, it uses a very short-lived dynamic memory allocation. Second, a `Vec` is a resizable object, which is useless in those context when random data have a fixed size and will only be read. `get_random_bytes()` takes a constant as a generic parameter and returns an array with the requested number of random bytes. Stack safety analysis: the random bytes will be allocated on the caller stack for a very short time (until the encoding function has been called on the data). In some cases, the random bytes take less room than the `Vec` did (a `Vec` is 24 bytes on a 64 bit computer). The maximum used size is 180 bytes, which makes it for 0.008% of the default stack size for a Rust thread (2MiB), so this is a non-issue. Also, most of the uses of those random bytes are to encode them using an `Encoding`. The function `crypto::encode_random_bytes()` generates random bytes and encode them with the provided `Encoding`, leading to code deduplication. `generate_id()` has also been converted to use a constant generic parameter as well since the length of the requested String is always a constant.
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BlackDex
approved these changes
Nov 11, 2022
jjlin
suggested changes
Nov 12, 2022
Its uses are replaced by get_randm_bytes() or encode_random_bytes().
BlackDex
approved these changes
Nov 15, 2022
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All uses of
get_random()were in the form of:&get_random(vec![0u8; SIZE])with
SIZEbeing a constant.Building a
Vecis unnecessary for two reasons. First, it uses a very short-lived dynamic memory allocation. Second, aVecis a resizable object, which is useless in those context when random data have a fixed size and will only be read.get_random_bytes()takes a constant as a generic parameter and returns an array with the requested number of random bytes.Stack safety analysis: the random bytes will be allocated on the caller stack for a very short time (until the encoding function has been called on the data). In some cases, the random bytes take less room than the
Vecdid (aVecis 24 bytes on a 64 bit computer). The maximum used size is 180 bytes, which makes it for 0.008% of the default stack size for a Rust thread (2MiB), so this is a non-issue.Also, most of the uses of those random bytes are to encode them using an
Encoding. The functioncrypto::encode_random_bytes()generates random bytes and encode them with the providedEncoding, leading to code deduplication.generate_id()has also been converted to use a constant generic parameter as well since the length of the requested String is always a constant.