[llvm] [z/OS] Add z/OS archive reading support (PR #187110)

[James Henderson via llvm-commits]

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@@ -1448,3 +1594,72 @@ BigArchive::BigArchive(MemoryBufferRef Source, Error &Err)
   setFirstRegular(*I);
   Err = Error::success();
 }
+
+ZOSArchive::ZOSArchive(MemoryBufferRef Source, Error &Err)
+    : Archive(Source, Err) {
+  ErrorAsOutParameter ErrAsOutParam(&Err);
+
+  // Get the special members.
+  child_iterator I = child_begin(Err, false);
+  if (Err)
+    return;
+  child_iterator E = child_end();
+
+  // See if this is a valid empty archive and if so return.
+  if (I == E) {
+    Err = Error::success();
+    return;
+  }
+  const Child *C = &*I;
+
+  Expected<StringRef> NameOrErr = C->getRawName();
+  if (!NameOrErr) {
+    Err = NameOrErr.takeError();
+    return;
+  }
+  StringRef Name = NameOrErr.get();
+
+  if (Name == "__.SYMDEF") {
+    // We know that the symbol table is not an external file, but we still must
+    // check any Expected<> return value.
+    Expected<StringRef> BufOrErr = C->getBuffer();
+    if (!BufOrErr) {
+      Err = BufOrErr.takeError();
+      return;
+    }
+
+    // Copy symbol table converting embedded EBCDIC names to ASCII.
+    StringRef ESymbolTable = BufOrErr.get();
+    uint32_t ESymbolCount = read32be(ESymbolTable.data());
+    uint32_t OffsetToENames =
+        sizeof(uint32_t) + (ESymbolCount * (sizeof(uint64_t)));
+    uint32_t ENamesSize = (uint32_t)ESymbolTable.size() - OffsetToENames;
+    const char *ENamesPtr = (const char *)ESymbolTable.data() + OffsetToENames;
----------------
jh7370 wrote:

Coding standards say that C-style cast here is inappropriate. You should only use them for numeric casts.

https://github.com/llvm/llvm-project/pull/187110