gdb: move store/extract integer functions to extract-store-integer.{c,h}

Move the declarations out of defs.h, and the implementations out of
findvar.c.

I opted for a new file, because this functionality of converting
integers to bytes and vice-versa seems a bit to generic to live in
findvar.c.

Change-Id: I524858fca33901ee2150c582bac16042148d2251
Approved-By: John Baldwin <jhb@FreeBSD.org>

1 files changed, 308 insertions, 0 deletions

diff --git a/gdb/extract-store-integer.c b/gdb/extract-store-integer.c
new file mode 100644
index 0000000..a3b7e40
--- /dev/null
+++ b/gdb/extract-store-integer.c
@@ -0,0 +1,308 @@
+/* Copyright (C) 2024 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "extract-store-integer.h"
+#include "gdbtypes.h"
+#include "gdbarch.h"
+#include "gdbsupport/selftest.h"
+
+template<typename T, typename>
+T
+extract_integer (gdb::array_view<const gdb_byte> buf, enum bfd_endian byte_order)
+{
+  typename std::make_unsigned<T>::type retval = 0;
+
+  if (buf.size () > (int) sizeof (T))
+    error (_("\
+That operation is not available on integers of more than %d bytes."),
+	   (int) sizeof (T));
+
+  /* Start at the most significant end of the integer, and work towards
+     the least significant.  */
+  if (byte_order == BFD_ENDIAN_BIG)
+    {
+      size_t i = 0;
+
+      if (std::is_signed<T>::value)
+	{
+	  /* Do the sign extension once at the start.  */
+	  retval = ((LONGEST) buf[i] ^ 0x80) - 0x80;
+	  ++i;
+	}
+      for (; i < buf.size (); ++i)
+	retval = (retval << 8) | buf[i];
+    }
+  else
+    {
+      ssize_t i = buf.size () - 1;
+
+      if (std::is_signed<T>::value)
+	{
+	  /* Do the sign extension once at the start.  */
+	  retval = ((LONGEST) buf[i] ^ 0x80) - 0x80;
+	  --i;
+	}
+      for (; i >= 0; --i)
+	retval = (retval << 8) | buf[i];
+    }
+  return retval;
+}
+
+/* Explicit instantiations.  */
+template LONGEST extract_integer<LONGEST> (gdb::array_view<const gdb_byte> buf,
+					   enum bfd_endian byte_order);
+template ULONGEST extract_integer<ULONGEST>
+  (gdb::array_view<const gdb_byte> buf, enum bfd_endian byte_order);
+
+/* Sometimes a long long unsigned integer can be extracted as a
+   LONGEST value.  This is done so that we can print these values
+   better.  If this integer can be converted to a LONGEST, this
+   function returns 1 and sets *PVAL.  Otherwise it returns 0.  */
+
+int
+extract_long_unsigned_integer (const gdb_byte *addr, int orig_len,
+			       enum bfd_endian byte_order, LONGEST *pval)
+{
+  const gdb_byte *p;
+  const gdb_byte *first_addr;
+  int len;
+
+  len = orig_len;
+  if (byte_order == BFD_ENDIAN_BIG)
+    {
+      for (p = addr;
+	   len > (int) sizeof (LONGEST) && p < addr + orig_len;
+	   p++)
+	{
+	  if (*p == 0)
+	    len--;
+	  else
+	    break;
+	}
+      first_addr = p;
+    }
+  else
+    {
+      first_addr = addr;
+      for (p = addr + orig_len - 1;
+	   len > (int) sizeof (LONGEST) && p >= addr;
+	   p--)
+	{
+	  if (*p == 0)
+	    len--;
+	  else
+	    break;
+	}
+    }
+
+  if (len <= (int) sizeof (LONGEST))
+    {
+      *pval = (LONGEST) extract_unsigned_integer (first_addr,
+						  sizeof (LONGEST),
+						  byte_order);
+      return 1;
+    }
+
+  return 0;
+}
+
+
+/* Treat the bytes at BUF as a pointer of type TYPE, and return the
+   address it represents.  */
+CORE_ADDR
+extract_typed_address (const gdb_byte *buf, struct type *type)
+{
+  gdb_assert (type->is_pointer_or_reference ());
+  return gdbarch_pointer_to_address (type->arch (), type, buf);
+}
+
+/* All 'store' functions accept a host-format integer and store a
+   target-format integer at ADDR which is LEN bytes long.  */
+template<typename T, typename>
+void
+store_integer (gdb::array_view<gdb_byte> dst, enum bfd_endian byte_order,
+	       T val)
+{
+  gdb_byte *p;
+  gdb_byte *startaddr = dst.data ();
+  gdb_byte *endaddr = startaddr + dst.size ();
+
+  /* Start at the least significant end of the integer, and work towards
+     the most significant.  */
+  if (byte_order == BFD_ENDIAN_BIG)
+    {
+      for (p = endaddr - 1; p >= startaddr; --p)
+	{
+	  *p = val & 0xff;
+	  val >>= 8;
+	}
+    }
+  else
+    {
+      for (p = startaddr; p < endaddr; ++p)
+	{
+	  *p = val & 0xff;
+	  val >>= 8;
+	}
+    }
+}
+
+/* Explicit instantiations.  */
+template void store_integer (gdb::array_view<gdb_byte> dst,
+			     bfd_endian byte_order, LONGEST val);
+
+template void store_integer (gdb::array_view<gdb_byte> dst,
+			     bfd_endian byte_order, ULONGEST val);
+
+/* Store the address ADDR as a pointer of type TYPE at BUF, in target
+   form.  */
+void
+store_typed_address (gdb_byte *buf, struct type *type, CORE_ADDR addr)
+{
+  gdb_assert (type->is_pointer_or_reference ());
+  gdbarch_address_to_pointer (type->arch (), type, buf, addr);
+}
+
+/* Copy a value from SOURCE of size SOURCE_SIZE bytes to DEST of size DEST_SIZE
+   bytes.  If SOURCE_SIZE is greater than DEST_SIZE, then truncate the most
+   significant bytes.  If SOURCE_SIZE is less than DEST_SIZE then either sign
+   or zero extended according to IS_SIGNED.  Values are stored in memory with
+   endianness BYTE_ORDER.  */
+
+void
+copy_integer_to_size (gdb_byte *dest, int dest_size, const gdb_byte *source,
+		      int source_size, bool is_signed,
+		      enum bfd_endian byte_order)
+{
+  signed int size_diff = dest_size - source_size;
+
+  /* Copy across everything from SOURCE that can fit into DEST.  */
+
+  if (byte_order == BFD_ENDIAN_BIG && size_diff > 0)
+    memcpy (dest + size_diff, source, source_size);
+  else if (byte_order == BFD_ENDIAN_BIG && size_diff < 0)
+    memcpy (dest, source - size_diff, dest_size);
+  else
+    memcpy (dest, source, std::min (source_size, dest_size));
+
+  /* Fill the remaining space in DEST by either zero extending or sign
+     extending.  */
+
+  if (size_diff > 0)
+    {
+      gdb_byte extension = 0;
+      if (is_signed
+	  && ((byte_order != BFD_ENDIAN_BIG && source[source_size - 1] & 0x80)
+	      || (byte_order == BFD_ENDIAN_BIG && source[0] & 0x80)))
+	extension = 0xff;
+
+      /* Extend into MSBs of SOURCE.  */
+      if (byte_order == BFD_ENDIAN_BIG)
+	memset (dest, extension, size_diff);
+      else
+	memset (dest + source_size, extension, size_diff);
+    }
+}
+
+#if GDB_SELF_TEST
+namespace selftests {
+
+/* Function to test copy_integer_to_size.  Store SOURCE_VAL with size
+   SOURCE_SIZE to a buffer, making sure no sign extending happens at this
+   stage.  Copy buffer to a new buffer using copy_integer_to_size.  Extract
+   copied value and compare to DEST_VALU.  Copy again with a signed
+   copy_integer_to_size and compare to DEST_VALS.  Do everything for both
+   LITTLE and BIG target endians.  Use unsigned values throughout to make
+   sure there are no implicit sign extensions.  */
+
+static void
+do_cint_test (ULONGEST dest_valu, ULONGEST dest_vals, int dest_size,
+	      ULONGEST src_val, int src_size)
+{
+  for (int i = 0; i < 2 ; i++)
+    {
+      gdb_byte srcbuf[sizeof (ULONGEST)] = {};
+      gdb_byte destbuf[sizeof (ULONGEST)] = {};
+      enum bfd_endian byte_order = i ? BFD_ENDIAN_BIG : BFD_ENDIAN_LITTLE;
+
+      /* Fill the src buffer (and later the dest buffer) with non-zero junk,
+	 to ensure zero extensions aren't hidden.  */
+      memset (srcbuf, 0xaa, sizeof (srcbuf));
+
+      /* Store (and later extract) using unsigned to ensure there are no sign
+	 extensions.  */
+      store_unsigned_integer (srcbuf, src_size, byte_order, src_val);
+
+      /* Test unsigned.  */
+      memset (destbuf, 0xaa, sizeof (destbuf));
+      copy_integer_to_size (destbuf, dest_size, srcbuf, src_size, false,
+			    byte_order);
+      SELF_CHECK (dest_valu == extract_unsigned_integer (destbuf, dest_size,
+							 byte_order));
+
+      /* Test signed.  */
+      memset (destbuf, 0xaa, sizeof (destbuf));
+      copy_integer_to_size (destbuf, dest_size, srcbuf, src_size, true,
+			    byte_order);
+      SELF_CHECK (dest_vals == extract_unsigned_integer (destbuf, dest_size,
+							 byte_order));
+    }
+}
+
+static void
+copy_integer_to_size_test ()
+{
+  /* Destination is bigger than the source, which has the signed bit unset.  */
+  do_cint_test (0x12345678, 0x12345678, 8, 0x12345678, 4);
+  do_cint_test (0x345678, 0x345678, 8, 0x12345678, 3);
+
+  /* Destination is bigger than the source, which has the signed bit set.  */
+  do_cint_test (0xdeadbeef, 0xffffffffdeadbeef, 8, 0xdeadbeef, 4);
+  do_cint_test (0xadbeef, 0xffffffffffadbeef, 8, 0xdeadbeef, 3);
+
+  /* Destination is smaller than the source.  */
+  do_cint_test (0x5678, 0x5678, 2, 0x12345678, 3);
+  do_cint_test (0xbeef, 0xbeef, 2, 0xdeadbeef, 3);
+
+  /* Destination and source are the same size.  */
+  do_cint_test (0x8765432112345678, 0x8765432112345678, 8, 0x8765432112345678,
+		8);
+  do_cint_test (0x432112345678, 0x432112345678, 6, 0x8765432112345678, 6);
+  do_cint_test (0xfeedbeaddeadbeef, 0xfeedbeaddeadbeef, 8, 0xfeedbeaddeadbeef,
+		8);
+  do_cint_test (0xbeaddeadbeef, 0xbeaddeadbeef, 6, 0xfeedbeaddeadbeef, 6);
+
+  /* Destination is bigger than the source.  Source is bigger than 32bits.  */
+  do_cint_test (0x3412345678, 0x3412345678, 8, 0x3412345678, 6);
+  do_cint_test (0xff12345678, 0xff12345678, 8, 0xff12345678, 6);
+  do_cint_test (0x432112345678, 0x432112345678, 8, 0x8765432112345678, 6);
+  do_cint_test (0xff2112345678, 0xffffff2112345678, 8, 0xffffff2112345678, 6);
+}
+
+} // namespace selftests
+
+#endif
+
+void _initialize_extract_store_integer ();
+void
+_initialize_extract_store_integer ()
+{
+#if GDB_SELF_TEST
+  selftests::register_test ("copy_integer_to_size",
+			    selftests::copy_integer_to_size_test);
+#endif
+}