adler32_combine64
Compute the Adler-32 of A followed by B with an explicit 64-bit length.
Full chapter and shared rules ↗57ad356e10ec68ee · Source at the matching commit ↗Read the function’s preconditions and results first. Expand the shared rules below for buffer and ownership requirements used throughout this API group.
uLong ZEXPORT adler32_combine64(uLong adler1, uLong adler2, z_off64_t len2);
Compute the Adler-32 of A followed by B with an explicit 64-bit length.
Domain Restricted domain. Effects: pure computation.
Pre For the concatenation result, the low 32 bits of adler1 and adler2
are the independently computed Adler-32 checksums of A and B, and len2 is the
length of B. Negative lengths are included for rejection.
Post Return 0xFFFFFFFF for a negative length. Otherwise return the
Adler-32 of A followed by B. Empty B leaves A's checksum unchanged.
Effects Preserve all memory and ownership. Read no buffers or stream state.
This has the same contract and length range as adler32_combine in LP64.
The explicit width matters on other builds; this page does not cover them.
Shared conditions and scope
API manual · Contract conventions · Buffer utilities
Compute a checksum a buffer at a time, or combine the checksums of independently processed byte sequences without rereading them. The byte sequences A and B below are ordinary data; the contracts use the Adler-32 or CRC-32 of those sequences.
| Task | Entries |
|---|---|
| Update Adler-32 | Size-type length, 32-bit length |
| Combine Adler-32 | Ordinary offset, explicit 64-bit offset |
| Update CRC-32 | Size-type length, 32-bit length |
| Combine CRC-32 | Ordinary offset, explicit 64-bit offset |
| Reuse a CRC combination operator | Generate, generate with 64-bit length, apply |
| Inspect the byte table | get_crc_table |
These focused contracts follow adler32.c, crc32.c and zlib.h in the default LP64 Linux
static build, with the pinned source and listed patches. Source readings are to confirm
by proof. No checksum entry writes state, allocates, frees or performs I/O. Exceptional
numeric results are ordinary values, rather than error codes. Domain and effects remain
independent as explained in contract conventions.
The practical checksum contracts use actual byte sequences A and B. Each checksum is computed independently, starting at 1 for Adler-32 or 0 for CRC-32. These contracts deliberately omit functional promises for forged checksums. The Lean targets also describe arbitrary seeds and exact scalar results. Both the Adler entries and their Lean targets require zero length for NULL initialization queries. See scope deviations and public goals.
In this build, uLong and z_size_t are unsigned 64-bit types; uInt is
unsigned 32-bit. z_off_t and z_off64_t are signed 64-bit. Input checksum bits
above bit 31 are ignored; returned checksums fit in 32 bits. The explicit
*64 declarations depend on the header's large-file feature macros.
Formal contract
ZlibF.Spec.Public.Goal.adler32_combine64
Proof status: Registered proof · Evidence and remaining work
/-- `uLong adler32_combine64(uLong adler1, uLong adler2, z_off64_t len2)`.
The LP64 64-bit-length entry has the same complete public combine contract. -/
def Goal.adler32_combine64 : Prop := AdlerCombine Zlib.Adler32.adler32_combine64