ppkarwasz opened a new pull request, #734:
URL: https://github.com/apache/commons-compress/pull/734
The 7z file format specification defines only **unsigned numbers**
(`UINT64`, `REAL_UINT64`, `UINT32`). However, the current implementation allows
parsing methods like `readUint64`, `getLong`, and `getInt` to return negative
values and then handles those inconsistently in downstream logic.
This PR introduces a safer and more specification-compliant number parsing
model.
### Key changes
* **Strict unsigned number parsing**
* Parsing methods now *never* return negative numbers.
* `readUint64`, `readUint64ToIntExact`, `readRealUint64`, and `readUint32`
follow the terminology from `7zFormat.txt`.
* Eliminates scattered negative-value checks that previously compensated
for parsing issues.
* **Improved header integrity validation**
* Before large allocations, the size is now validated against the **actual
available data in the header** as well as the memory limit.
* Prevents unnecessary or unsafe allocations when the archive is corrupted
or truncated.
* **Correct numeric type usage**
* Some fields represent 7z numbers as 64-bit values but are constrained
internally to Java `int` limits.
* These are now declared as `int` to signal real constraints in our
implementation.
* **Consistent error handling** Parsing now throws only three well-defined
exception types:
| Condition |
Exception |
| ---------------------------------------------------------------------- |
-------------------------------------------- |
| Declared structure exceeds `maxMemoryLimitKiB` |
`MemoryLimitException` |
| Missing data inside header (truncated or corrupt) |
`ArchiveException("Corrupted 7z archive")` |
| Unsupported numeric values (too large for implementation) |
`ArchiveException("Unsupported 7z archive")` |
Note: `EOFException` is no longer used: a header with missing fields is
not “EOF,” it is **corrupted**.
This PR lays groundwork for safer parsing and easier future maintenance by
aligning number handling with the actual 7z specification and making header
parsing behavior *predictable and robust*.
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