pjfanning opened a new pull request, #1289:
URL: https://github.com/apache/poi/pull/1289
`places` was accepted unbounded: `=DEC2HEX(1E10,1E10)` built a 2 GB padding
string through `String.format("%0NX")` and ran out of memory (a denial of
service by formula content), and `=DEC2HEX(255,11)` returned `000000000FF`.
Excel accepts 1–10 places and returns `#NUM!` otherwise, or when the result
needs more characters than `places`.
| Formula | Before | After (Excel) |
|---|---|---|
| `=DEC2HEX(255,1E10)` | `OutOfMemoryError` | `#NUM!` |
| `=DEC2HEX(255,11)` | `000000000FF` | `#NUM!` |
| `=DEC2HEX(255,1)` | `FF` | `#NUM!` |
| `=DEC2HEX(100,0)` | `64` | `#NUM!` |
| `=DEC2BIN(9,8)` | `1001` | `00001001` |
| `=DEC2HEX(-549755813888)` | `FF80000000` | `8000000000` |
| `=DEC2HEX(549755813887,10)` | `FFFFFFFFFF` | `7FFFFFFFFF` |
Fixed on the way, since the rewrite touched the same lines:
- `DEC2BIN` never zero-padded to `places` — two existing tests had the wrong
value marked `TODO: documentation and behavior do not match here!`; they now
assert the documented result.
- Negative numbers were rendered through an `int` cast
(`number.intValue()`), so anything below `Integer.MIN_VALUE` was wrong; both
functions now mask to the 40-bit / 10-bit two's complement Excel documents.
Positive numbers above the int range with `places` had the same cast.
- A non-integer `number` is truncated toward zero over the whole range
(`DEC2HEX(-0.9)` = `0`, `DEC2BIN(511.9)` = `111111111`, `DEC2BIN(512.5)` =
`#NUM!`).
One existing expectation changes: `DEC2HEX(100,0)` was `64` and is now
`#NUM!`, which is what Excel gives for zero places (the `DEC2BIN`
implementation already did this).
`DEC2OCT` is not implemented in POI, so nothing to do there.
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