diff --git a/toolkit/components/osfile/osfileutils.cpp b/toolkit/components/osfile/osfileutils.cpp
new file mode 100644
index 000000000000..0950924c76f5
--- /dev/null
+++ b/toolkit/components/osfile/osfileutils.cpp
@@ -0,0 +1,194 @@
+
+#include "mozilla/Scoped.h"
+
+#include "osfileutils.h"
+#include "nsICharsetConverterManager.h"
+#include "nsServiceManagerUtils.h"
+#include "nsCOMPtr.h"
+#include "nsCRTGlue.h"
+
+// Utilities for handling errors
+namespace {
+
+#if defined(XP_WIN)
+#include <Windows.h>
+
+/**
+ * Set the OS-specific error to inform the OS that
+ * the last operation failed because it is not supported.
+ */
+void error_not_supported() {
+  SetLastError(ERROR_NOT_SUPPORTED);
+}
+
+/**
+ * Set the OS-specific error to inform the OS that
+ * the last operation failed because of an invalid
+ * argument.
+ */
+void error_invalid_argument() {
+  SetLastError(ERROR_INVALID_DATA);
+}
+
+/**
+ * Set the OS-specific error to inform the OS that
+ * the last operation failed because of insufficient
+ * memory.
+ */
+void error_no_memory() {
+  SetLastError(ERROR_NOT_ENOUGH_MEMORY);
+}
+
+#else
+
+#include "errno.h"
+
+/**
+ * Set the OS-specific error to inform the OS that
+ * the last operation failed because it is not supported.
+ */
+void error_not_supported() {
+  errno = ENOTSUP;
+}
+
+/**
+ * Set the OS-specific error to inform the OS that
+ * the last operation failed because of an invalid
+ * argument.
+ */
+void error_invalid_argument() {
+  errno = EINVAL;
+}
+
+/**
+ * Set the OS-specific error to inform the OS that
+ * the last operation failed because of insufficient
+ * memory.
+ */
+void error_no_memory() {
+  errno = ENOMEM;
+}
+
+#endif // defined(XP_WIN)
+
+}
+
+
+extern "C" {
+
+// Memory utilities
+
+MOZ_EXPORT_API(void) osfile_ns_free(void* buf) {
+  NS_Free(buf);
+}
+
+// Unicode utilities
+
+MOZ_EXPORT_API(PRUnichar*) osfile_wstrdup(PRUnichar* string) {
+  return NS_strdup(string);
+}
+
+MOZ_EXPORT_API(PRUnichar*) osfile_DecodeAll(
+   const char* aEncoding,
+   const char* aSource,
+   const int32_t aBytesToDecode)
+{
+  if (!aEncoding || !aSource) {
+    error_invalid_argument();
+    return nsnull;
+  }
+
+  nsresult rv;
+  nsCOMPtr<nsICharsetConverterManager> manager =
+    do_GetService(NS_CHARSETCONVERTERMANAGER_CONTRACTID, &rv);
+  if (NS_FAILED(rv)) {
+    error_not_supported();
+    return nsnull;
+  }
+
+  nsCOMPtr<nsIUnicodeDecoder> decoder;
+  rv = manager->GetUnicodeDecoder(aEncoding, getter_AddRefs(decoder));
+  if (NS_FAILED(rv)) {
+    error_invalid_argument();
+    return nsnull;
+  }
+
+  // Compute an upper bound to the number of chars, allocate buffer
+
+  int32_t srcBytes = aBytesToDecode;
+  int32_t upperBoundChars = 0;
+  rv = decoder->GetMaxLength(aSource, srcBytes, &upperBoundChars);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+  int32_t bufSize = (upperBoundChars + 1) * sizeof (PRUnichar);
+
+  mozilla::ScopedFreePtr<PRUnichar> dest((PRUnichar*)NS_Alloc(bufSize));
+  if (dest.get() == nsnull) {
+    error_no_memory();
+    return nsnull;
+  }
+
+  // Convert, add trailing \0
+
+  rv = decoder->Convert(aSource, &srcBytes, dest.rwget(), &upperBoundChars);
+  if (NS_FAILED(rv)) {
+    error_invalid_argument();
+    return nsnull;
+  }
+
+  dest.rwget()[upperBoundChars] = '\0';
+
+  return dest.forget();
+}
+
+MOZ_EXPORT_API(char*) osfile_EncodeAll(
+   const char* aEncoding,
+   const PRUnichar* aSource,
+   int32_t* aBytesProduced)
+{
+  if (!aEncoding || !aSource || !aBytesProduced) {
+    error_invalid_argument();
+    return nsnull;
+  }
+
+  nsresult rv;
+  nsCOMPtr<nsICharsetConverterManager> manager =
+    do_GetService(NS_CHARSETCONVERTERMANAGER_CONTRACTID, &rv);
+  if (NS_FAILED(rv)) {
+    error_not_supported();
+    return nsnull;
+  }
+
+  nsCOMPtr<nsIUnicodeEncoder> encoder;
+  rv = manager->GetUnicodeEncoder(aEncoding, getter_AddRefs(encoder));
+  if (NS_FAILED(rv)) {
+    error_invalid_argument();
+    return nsnull;
+  }
+
+  int32_t srcChars = NS_strlen(aSource);
+
+  int32_t upperBoundBytes = 0;
+  rv = encoder->GetMaxLength(aSource, srcChars, &upperBoundBytes);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+  printf_stderr("Encoding %d chars into at up to %d bytes\n", srcChars, upperBoundBytes);
+  int32_t bufSize = upperBoundBytes;
+  mozilla::ScopedFreePtr<char> dest((char*)NS_Alloc(bufSize));
+
+  if (dest.get() == nsnull) {
+    error_no_memory();
+    return nsnull;
+  }
+
+  rv = encoder->Convert(aSource, &srcChars, dest.rwget(), &upperBoundBytes);
+  if (NS_FAILED(rv)) {
+    error_invalid_argument();
+    return nsnull;
+  }
+
+  *aBytesProduced = upperBoundBytes;
+  return dest.forget();
+}
+
+} // extern "C"
diff --git a/toolkit/components/osfile/osfileutils.h b/toolkit/components/osfile/osfileutils.h
new file mode 100644
index 000000000000..fe3be9a5d852
--- /dev/null
+++ b/toolkit/components/osfile/osfileutils.h
@@ -0,0 +1,65 @@
+#ifndef mozilla_osfileutils_h__
+#define mozilla_osfileutils_h__
+
+#include "mozilla/Types.h"
+#include "nsIUnicodeDecoder.h"
+#include "nsIUnicodeEncoder.h"
+
+extern "C" {
+
+// Memory utilities
+
+/**
+ * As |NS_Free|, but exported.
+ */
+MOZ_EXPORT_API(void) osfile_ns_free(void* buf);
+
+// Unicode utilities
+
+/**
+ * Duplicate a Unicode string, as per wpcpy/StrDupW.
+ *
+ * @param source A well-formed, nul-terminated, Unicode string.
+ *
+ * @return Either |NULL| if there was not enough memory to copy the
+ * string, or a new string with the same contents as |source|.
+ * Memory MUST be released with |osfile_ns_free|.
+ */
+MOZ_EXPORT_API(PRUnichar*) osfile_wstrdup(PRUnichar* source);
+
+/**
+ * Decode a nul-terminated C string into a Unicode string.
+ *
+ * @param aEncoding The encoding to use.
+ * @param aSource The C string to decode.
+ * @param aBytesToDecode The number of bytes to decode from |aSource|.
+ *
+ * @return null in case of error, otherwise a sequence of Unicode
+ *   chars, representing |aSource|. This memory MUST be released with
+ *   |NS_Free|/|osfile_ns_free|.
+ */
+MOZ_EXPORT_API(PRUnichar*) osfile_DecodeAll(
+   const char* aEncoding,
+   const char* aSource,
+   const int32_t aBytesToDecode);
+
+/**
+ * Encode a complete Unicode string into a set of bytes.
+ *
+ * @param aEncoding The encoding to use.
+ * @param aSource The Unicode string to encode. Must be nul-terminated.
+ * @param aBytesWritten (out) The number of bytes encoded.
+ *
+ * @return null in case of error, otherwise a new buffer.  The
+ * number of bytes actually allocated may be higher than
+ * |aBytesWritten|.  The buffer MUST be released with
+ * |NS_Free|/|osfile_ns_free|.
+ */
+MOZ_EXPORT_API(char*) osfile_EncodeAll(
+   const char* aEncoding,
+   const PRUnichar* aSource,
+   int32_t* aBytesWritten);
+
+} // extern "C"
+
+#endif // mozilla_osfileutils_h__