util: Add rust-base62 implementation from rustc

Author: CohenArthur

gcc/rust/Make-lang.in

@@ -88,6 +88,7 @@ GRS_OBJS = \
     rust/rust-lint-marklive.o \
     rust/rust-hir-type-check-path.o \
     rust/rust-compile-intrinsic.o \
+    rust/rust-base62.o \
     $(END)
 # removed object files from here
 

gcc/rust/backend/rust-mangle.cc

@@ -1,5 +1,6 @@
 #include "rust-mangle.h"
 #include "fnv-hash.h"
+#include "rust-base62.h"
 #include <algorithm>
 
 // FIXME: Rename those to legacy_*
@@ -155,28 +156,6 @@ v0_simple_type_prefix (const TyTy::BaseType *ty)
   gcc_unreachable ();
 }
 
-// FIXME: Is this present somewhere in libbiberty already?
-static std::string
-v0_base62_integer (uint64_t x)
-{
-  const static std::string base_64
-    = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@$";
-  std::string buffer (128, '\0');
-  size_t idx = 0;
-  size_t base = 62;
-
-  do
-    {
-      buffer[idx] = base_64[(x % base)];
-      idx++;
-      x = x / base;
-    }
-  while (x != 0);
-
-  std::reverse (buffer.begin (), buffer.begin () + idx);
-  return buffer.substr (0, idx);
-}
-
 // Add an underscore-terminated base62 integer to the mangling string.
 // This corresponds to the `<base-62-number>` grammar in the v0 mangling RFC:
 //  - 0 is encoded as "_"
@@ -185,7 +164,7 @@ static void
 v0_add_integer_62 (std::string &mangled, uint64_t x)
 {
   if (x > 0)
-    mangled.append (v0_base62_integer (x - 1));
+    mangled.append (base62_integer (x - 1));
 
   mangled.append ("_");
 }

gcc/rust/util/rust-base62.cc

@@ -0,0 +1,30 @@
+#include "rust-base62.h"
+
+#include <algorithm>
+
+namespace Rust {
+
+std::string
+base62_integer (uint64_t value)
+{
+  const static std::string base_64
+    = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@$";
+  std::string buffer (128, '\0');
+  size_t idx = 0;
+  size_t base = 62;
+
+  do
+    {
+      buffer[idx] = base_64[(value % base)];
+      idx++;
+      value = value / base;
+    }
+  while (value != 0);
+
+  std::reverse (buffer.begin (), buffer.begin () + idx);
+  return buffer.substr (0, idx);
+}
+
+} // namespace Rust
+
+// FIXME: Add unit testing using the selftest framework

gcc/rust/util/rust-base62.h

@@ -0,0 +1,16 @@
+#ifndef RUST_BASE62_H
+#define RUST_BASE62_H
+
+#include <string>
+
+namespace Rust {
+
+/**
+ * Get the Base62 representation of an integer
+ */
+std::string
+base62_integer (uint64_t value);
+
+} // namespace Rust
+
+#endif /* !RUST_BASE62_H */