Function read_scriptint

pub fn read_scriptint(v: &[u8]) -> Result<i64, Error>

Decodes an integer in script(minimal CScriptNum) format.

Notice that this fails on overflow: the result is the same as in bitcoind, that only 4-byte signed-magnitude values may be read as numbers. They can be added or subtracted (and a long time ago, multiplied and divided), and this may result in numbers which can’t be written out in 4 bytes or less. This is ok! The number just can’t be read as a number again. This is a bit crazy and subtle, but it makes sense: you can load 32-bit numbers and do anything with them, which back when mult/div was allowed, could result in up to a 64-bit number. We don’t want overflow since that’s surprising — and we don’t want numbers that don’t fit in 64 bits (for efficiency on modern processors) so we simply say, anything in excess of 32 bits is no longer a number. This is basically a ranged type implementation.

This code is based on the CScriptNum constructor in Bitcoin Core (see script.h).