chore(asm): use parameternamelength for libddwaf interface [backport …

…2.12] (#10604)

Backport 97fa6d6 from #10596 to 2.12.

This is a minor improvement for the libddwaf interface, applying the
same idea in #10438 to
parameter strings.

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Co-authored-by: Christophe Papazian <[email protected]>
Co-authored-by: Alberto Vara <[email protected]>

ddtrace/appsec/_ddwaf/ddwaf_types.py

@@ -184,8 +184,8 @@ def struct(self) -> DDWafRulesType:
             return self.value.stringValue[: self.nbEntries].decode("UTF-8", errors="ignore")
         if self.type == DDWAF_OBJ_TYPE.DDWAF_OBJ_MAP:
             return {
-                self.value.array[i].parameterName.decode("UTF-8", errors="ignore"): self.value.array[i].struct
-                for i in range(self.nbEntries)
+                obj.parameterName[: obj.parameterNameLength].decode("UTF-8", errors="ignore"): obj.struct
+                for obj in self.value.array[: self.nbEntries]
             }
         if self.type == DDWAF_OBJ_TYPE.DDWAF_OBJ_ARRAY:
             return [self.value.array[i].struct for i in range(self.nbEntries)]
@@ -221,7 +221,7 @@ class ddwaf_value(ctypes.Union):
 
 
 ddwaf_object._fields_ = [
-    ("parameterName", ctypes.c_char_p),
+    ("parameterName", ctypes.POINTER(ctypes.c_char)),
     ("parameterNameLength", ctypes.c_uint64),
     ("value", ddwaf_value),
     ("nbEntries", ctypes.c_uint64),