std.zlib

The system zlib through its one-shot C interface: the zlib stream of a whole view, and the CRC-32 and Adler-32 checksums that PNG files and zlib streams carry. Importing this module links -lz (its row in projects/toolchain.py); the library is found where the C compiler finds it, and nothing is downloaded. zlib's streaming interface keeps pointers into the caller's buffers inside a z_stream, which a second-class borrow cannot be, so only the calls that take a pointer and a length for the length of the call are bound. Cost: one foreign call each, ffi:<symbol> in every caller's row, and the output Vec's allocation.

// zlib's own code: -2 a level outside -1..9, -4 out of memory, -5 a destination too small.
pub struct ZError { code:i32; }

// The zlib stream (RFC 1950) of `data` at `level`: 0 stores, 1 is fastest, 9 is smallest, -1 is zlib's default.
// effects: alloc, ffi:compress2, ffi:compressBound, ffi_precondition, free, local_write, read:data, trap, zero_init
pub fn compress(n:usize, data:ro<u8>[n]@host, level:i32) -> std.core.Result[std.vec.Vec[u8], std.zlib.ZError]

// The CRC-32 of `data` continued from `crc`; start a new one from 0.
pub fn crc32(crc:u32, n:usize, data:ro<u8>[n]@host) -> u32  // effects: ffi:crc32_z, ffi_precondition, read:data, trap

// The Adler-32 of `data` continued from `adler`; start a new one from 1.
// effects: ffi:adler32_z, ffi_precondition, read:data, trap
pub fn adler32(adler:u32, n:usize, data:ro<u8>[n]@host) -> u32

A generic function's effects are what it may do for any arguments within its bounds, besides what their own trait members do.