rtmessage: fix potential divide by zero in rtHashMap_Hash_Func_String

[svc-rdkeportal01]

Issue Fixed

Coverity Defect: DIVIDE_BY_ZERO
CWE: CWE-369 (Divide By Zero)
Severity: High
Function: rtHashMap_Hash_Func_String
File: src/rtmessage/rtHashMap.c

Root Cause

The function rtHashMap_Hash_Func_String computes a hash value and uses modulo to map it to a bucket:

return abs(hash) % rtVector_Size(hashmap->buckets);

If rtVector_Size(hashmap->buckets) returns 0 (empty buckets vector), this causes a divide by zero error, which will crash the program.

Changes Made

Before (Buggy):

while(*skey)
{
    hash = hash * 31 + *skey;
    skey++;
}
return abs(hash) % rtVector_Size(hashmap->buckets);  // ❌ Can divide by zero!

After (Fixed):

while(*skey)
{
    hash = hash * 31 + *skey;
    skey++;
}
size_t buckets_size = rtVector_Size(hashmap->buckets);
if(buckets_size == 0)  // ✅ Check for zero
    return 0;
return abs(hash) % buckets_size;  // ✅ Safe to divide

Why This Fix is Correct

1. Prevents crash - Checks for zero before division
2. Reasonable fallback - Returns 0 when buckets are empty (no valid bucket index exists)
3. Minimal change - Just adds a safety check
4. Performance - Negligible overhead (one comparison)

Edge Case Handling

When does buckets_size == 0?

• HashMap is newly created but not initialized
• HashMap has been cleared/destroyed
• Corrupted state

Why return 0?

• When there are no buckets, there's no valid bucket index
• Returning 0 is a safe default (will be handled by caller)
• Prevents undefined behavior from division by zero

Testing

• Verified fix compiles without errors
• Checked that zero case is properly handled
• Confirmed normal operation is unaffected