Function deflateInit_

#[export_name = "deflateInit_"]
pub unsafe extern "C-unwind" fn deflateInit_(
    strm: z_streamp,
    level: c_int,
    version: *const c_char,
    stream_size: c_int,
) -> c_int

Initializes the state for compression

The stream’s zalloc, zfree and opaque fields must be initialized before by the caller. If zalloc and zfree are set to NULL, deflateInit_ updates them to use default allocation functions. The total_in, total_out, adler, and msg fields are initialized.

The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:

• level 0 gives no compression at all (the input data is simply copied a block at a time)
• level 1 gives best speed
• level 9 gives best compression
• Z_DEFAULT_COMPRESSION requests a default compromise between speed and compression (currently equivalent to level 6).

A call to inflateInit_ is equivalent to inflateInit2_ where

• method is 8 (deflate)
• windowBits is 15
• memLevel is 8
• strategy is 0 (default)

Returns

• Z_OK if success
• Z_MEM_ERROR if there was not enough memory
• Z_VERSION_ERROR if the zlib library version is incompatible with the version assumed by the caller
• Z_STREAM_ERROR if a parameter is invalid, such as a null pointer to the structure

Safety

The caller must guarantee that

• Either
  • strm is NULL
  • strm satisfies the requirements of &mut *strm
• Either
  • version is NULL
  • version satisfies the requirements of core::ffi::CStr::from_ptr
• If strm is not NULL, the following fields contain valid values
  • zalloc
  • zfree
  • opaque

Example

use core::mem::MaybeUninit;
use libz_rs_sys::{z_stream, deflateInit_, zlibVersion, Z_OK};

// the zalloc and zfree fields are initialized as zero/NULL.
// `deflateInit_` will set a default allocation  and deallocation function.
let mut strm = MaybeUninit::zeroed();

let err = unsafe {
    deflateInit_(
        strm.as_mut_ptr(),
        6,
        zlibVersion(),
        core::mem::size_of::<z_stream>() as _,
    )
};
assert_eq!(err, Z_OK);

// the stream is now fully initialized. Prefer `assume_init_mut` over
// `assume_init` so the stream does not get moved.
let strm = unsafe { strm.assume_init_mut() };