Module script

Bitcoin scripts.

Scripts define Bitcoin’s digital signature scheme: a signature is formed from a script (the second half of which is defined by a coin to be spent, and the first half provided by the spending transaction), and is valid iff the script leaves TRUE on the stack after being evaluated. Bitcoin’s script is a stack-based assembly language similar in spirit to Forth.

This module provides the structures and functions needed to support scripts.

Structs

• Builder
  An object which can be used to construct a script piece by piece.
• Instructions
  Iterator over a script returning parsed opcodes.
• Script
  Bitcoin script.

Enums

• Error
  Ways that a script might fail. Not everything is split up as much as it could be; patches welcome if more detailed errors would help you.
• Instruction
  A “parsed opcode” which allows iterating over a Script in a more sensible way.

Functions

• read_scriptbool
  This is like “read_scriptint then map 0 to false and everything else as true”, except that the overflow rules don’t apply.
• read_scriptint
  Helper to decode an integer in script 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.
• read_uint
  Read a script-encoded unsigned integer