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diff --git a/deps/libchdr/deps/zstd-1.5.5/contrib/diagnose_corruption/check_flipped_bits.c b/deps/libchdr/deps/zstd-1.5.5/contrib/diagnose_corruption/check_flipped_bits.c
new file mode 100644
index 00000000..09ddd467
--- /dev/null
+++ b/deps/libchdr/deps/zstd-1.5.5/contrib/diagnose_corruption/check_flipped_bits.c
@@ -0,0 +1,400 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+
+#define ZSTD_STATIC_LINKING_ONLY
+#include "zstd.h"
+#include "zstd_errors.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+typedef struct {
+  char *input;
+  size_t input_size;
+
+  char *perturbed; /* same size as input */
+
+  char *output;
+  size_t output_size;
+
+  const char *dict_file_name;
+  const char *dict_file_dir_name;
+  int32_t dict_id;
+  char *dict;
+  size_t dict_size;
+  ZSTD_DDict* ddict;
+
+  ZSTD_DCtx* dctx;
+
+  int success_count;
+  int error_counts[ZSTD_error_maxCode];
+} stuff_t;
+
+static void free_stuff(stuff_t* stuff) {
+  free(stuff->input);
+  free(stuff->output);
+  ZSTD_freeDDict(stuff->ddict);
+  free(stuff->dict);
+  ZSTD_freeDCtx(stuff->dctx);
+}
+
+static void usage(void) {
+  fprintf(stderr, "check_flipped_bits input_filename [-d dict] [-D dict_dir]\n");
+  fprintf(stderr, "\n");
+  fprintf(stderr, "Arguments:\n");
+  fprintf(stderr, "    -d file: path to a dictionary file to use.\n");
+  fprintf(stderr, "    -D dir : path to a directory, with files containing dictionaries, of the\n"
+                  "             form DICTID.zstd-dict, e.g., 12345.zstd-dict.\n");
+  exit(1);
+}
+
+static void print_summary(stuff_t* stuff) {
+  int error_code;
+  fprintf(stderr, "%9d successful decompressions\n", stuff->success_count);
+  for (error_code = 0; error_code < ZSTD_error_maxCode; error_code++) {
+    int count = stuff->error_counts[error_code];
+    if (count) {
+      fprintf(
+          stderr, "%9d failed decompressions with message: %s\n",
+          count, ZSTD_getErrorString(error_code));
+    }
+  }
+}
+
+static char* readFile(const char* filename, size_t* size) {
+  struct stat statbuf;
+  int ret;
+  FILE* f;
+  char *buf;
+  size_t bytes_read;
+
+  ret = stat(filename, &statbuf);
+  if (ret != 0) {
+    fprintf(stderr, "stat failed: %m\n");
+    return NULL;
+  }
+  if ((statbuf.st_mode & S_IFREG) != S_IFREG) {
+    fprintf(stderr, "Input must be regular file\n");
+    return NULL;
+  }
+
+  *size = statbuf.st_size;
+
+  f = fopen(filename, "r");
+  if (f == NULL) {
+    fprintf(stderr, "fopen failed: %m\n");
+    return NULL;
+  }
+
+  buf = malloc(*size);
+  if (buf == NULL) {
+    fprintf(stderr, "malloc failed\n");
+    fclose(f);
+    return NULL;
+  }
+
+  bytes_read = fread(buf, 1, *size, f);
+  if (bytes_read != *size) {
+    fprintf(stderr, "failed to read whole file\n");
+    fclose(f);
+    free(buf);
+    return NULL;
+  }
+
+  ret = fclose(f);
+  if (ret != 0) {
+    fprintf(stderr, "fclose failed: %m\n");
+    free(buf);
+    return NULL;
+  }
+
+  return buf;
+}
+
+static ZSTD_DDict* readDict(const char* filename, char **buf, size_t* size, int32_t* dict_id) {
+  ZSTD_DDict* ddict;
+  *buf = readFile(filename, size);
+  if (*buf == NULL) {
+    fprintf(stderr, "Opening dictionary file '%s' failed\n", filename);
+    return NULL;
+  }
+
+  ddict = ZSTD_createDDict_advanced(*buf, *size, ZSTD_dlm_byRef, ZSTD_dct_auto, ZSTD_defaultCMem);
+  if (ddict == NULL) {
+    fprintf(stderr, "Failed to create ddict.\n");
+    return NULL;
+  }
+  if (dict_id != NULL) {
+    *dict_id = ZSTD_getDictID_fromDDict(ddict);
+  }
+  return ddict;
+}
+
+static ZSTD_DDict* readDictByID(stuff_t *stuff, int32_t dict_id, char **buf, size_t* size) {
+  if (stuff->dict_file_dir_name == NULL) {
+    return NULL;
+  } else {
+    size_t dir_name_len = strlen(stuff->dict_file_dir_name);
+    int dir_needs_separator = 0;
+    size_t dict_file_name_alloc_size = dir_name_len + 1 /* '/' */ + 10 /* max int32_t len */ + strlen(".zstd-dict") + 1 /* '\0' */;
+    char *dict_file_name = malloc(dict_file_name_alloc_size);
+    ZSTD_DDict* ddict;
+    int32_t read_dict_id;
+    if (dict_file_name == NULL) {
+      fprintf(stderr, "malloc failed.\n");
+      return 0;
+    }
+
+    if (dir_name_len > 0 && stuff->dict_file_dir_name[dir_name_len - 1] != '/') {
+      dir_needs_separator = 1;
+    }
+
+    snprintf(
+      dict_file_name,
+      dict_file_name_alloc_size,
+      "%s%s%u.zstd-dict",
+      stuff->dict_file_dir_name,
+      dir_needs_separator ? "/" : "",
+      dict_id);
+
+    /* fprintf(stderr, "Loading dict %u from '%s'.\n", dict_id, dict_file_name); */
+
+    ddict = readDict(dict_file_name, buf, size, &read_dict_id);
+    if (ddict == NULL) {
+      fprintf(stderr, "Failed to create ddict from '%s'.\n", dict_file_name);
+      free(dict_file_name);
+      return 0;
+    }
+    if (read_dict_id != dict_id) {
+      fprintf(stderr, "Read dictID (%u) does not match expected (%u).\n", read_dict_id, dict_id);
+      free(dict_file_name);
+      ZSTD_freeDDict(ddict);
+      return 0;
+    }
+
+    free(dict_file_name);
+    return ddict;
+  }
+}
+
+static int init_stuff(stuff_t* stuff, int argc, char *argv[]) {
+  const char* input_filename;
+
+  if (argc < 2) {
+    usage();
+  }
+
+  input_filename = argv[1];
+  stuff->input_size = 0;
+  stuff->input = readFile(input_filename, &stuff->input_size);
+  if (stuff->input == NULL) {
+    fprintf(stderr, "Failed to read input file.\n");
+    return 0;
+  }
+
+  stuff->perturbed = malloc(stuff->input_size);
+  if (stuff->perturbed == NULL) {
+    fprintf(stderr, "malloc failed.\n");
+    return 0;
+  }
+  memcpy(stuff->perturbed, stuff->input, stuff->input_size);
+
+  stuff->output_size = ZSTD_DStreamOutSize();
+  stuff->output = malloc(stuff->output_size);
+  if (stuff->output == NULL) {
+    fprintf(stderr, "malloc failed.\n");
+    return 0;
+  }
+
+  stuff->dict_file_name = NULL;
+  stuff->dict_file_dir_name = NULL;
+  stuff->dict_id = 0;
+  stuff->dict = NULL;
+  stuff->dict_size = 0;
+  stuff->ddict = NULL;
+
+  if (argc > 2) {
+    if (!strcmp(argv[2], "-d")) {
+      if (argc > 3) {
+        stuff->dict_file_name = argv[3];
+      } else {
+        usage();
+      }
+    } else
+    if (!strcmp(argv[2], "-D")) {
+      if (argc > 3) {
+        stuff->dict_file_dir_name = argv[3];
+      } else {
+        usage();
+      }
+    } else {
+      usage();
+    }
+  }
+
+  if (stuff->dict_file_dir_name) {
+    int32_t dict_id = ZSTD_getDictID_fromFrame(stuff->input, stuff->input_size);
+    if (dict_id != 0) {
+      stuff->ddict = readDictByID(stuff, dict_id, &stuff->dict, &stuff->dict_size);
+      if (stuff->ddict == NULL) {
+        fprintf(stderr, "Failed to create cached ddict.\n");
+        return 0;
+      }
+      stuff->dict_id = dict_id;
+    }
+  } else
+  if (stuff->dict_file_name) {
+    stuff->ddict = readDict(stuff->dict_file_name, &stuff->dict, &stuff->dict_size, &stuff->dict_id);
+    if (stuff->ddict == NULL) {
+      fprintf(stderr, "Failed to create ddict from '%s'.\n", stuff->dict_file_name);
+      return 0;
+    }
+  }
+
+  stuff->dctx = ZSTD_createDCtx();
+  if (stuff->dctx == NULL) {
+    return 0;
+  }
+
+  stuff->success_count = 0;
+  memset(stuff->error_counts, 0, sizeof(stuff->error_counts));
+
+  return 1;
+}
+
+static int test_decompress(stuff_t* stuff) {
+  size_t ret;
+  ZSTD_inBuffer in = {stuff->perturbed, stuff->input_size, 0};
+  ZSTD_outBuffer out = {stuff->output, stuff->output_size, 0};
+  ZSTD_DCtx* dctx = stuff->dctx;
+  int32_t custom_dict_id = ZSTD_getDictID_fromFrame(in.src, in.size);
+  char *custom_dict = NULL;
+  size_t custom_dict_size = 0;
+  ZSTD_DDict* custom_ddict = NULL;
+
+  if (custom_dict_id != 0 && custom_dict_id != stuff->dict_id) {
+    /* fprintf(stderr, "Instead of dict %u, this perturbed blob wants dict %u.\n", stuff->dict_id, custom_dict_id); */
+    custom_ddict = readDictByID(stuff, custom_dict_id, &custom_dict, &custom_dict_size);
+  }
+
+  ZSTD_DCtx_reset(dctx, ZSTD_reset_session_only);
+
+  if (custom_ddict != NULL) {
+    ZSTD_DCtx_refDDict(dctx, custom_ddict);
+  } else {
+    ZSTD_DCtx_refDDict(dctx, stuff->ddict);
+  }
+
+  while (in.pos != in.size) {
+    out.pos = 0;
+    ret = ZSTD_decompressStream(dctx, &out, &in);
+
+    if (ZSTD_isError(ret)) {
+      unsigned int code = ZSTD_getErrorCode(ret);
+      if (code >= ZSTD_error_maxCode) {
+        fprintf(stderr, "Received unexpected error code!\n");
+        exit(1);
+      }
+      stuff->error_counts[code]++;
+      /*
+      fprintf(
+          stderr, "Decompression failed: %s\n", ZSTD_getErrorName(ret));
+      */
+      if (custom_ddict != NULL) {
+        ZSTD_freeDDict(custom_ddict);
+        free(custom_dict);
+      }
+      return 0;
+    }
+  }
+
+  stuff->success_count++;
+
+  if (custom_ddict != NULL) {
+    ZSTD_freeDDict(custom_ddict);
+    free(custom_dict);
+  }
+  return 1;
+}
+
+static int perturb_bits(stuff_t* stuff) {
+  size_t pos;
+  size_t bit;
+  for (pos = 0; pos < stuff->input_size; pos++) {
+    unsigned char old_val = stuff->input[pos];
+    if (pos % 1000 == 0) {
+      fprintf(stderr, "Perturbing byte %zu / %zu\n", pos, stuff->input_size);
+    }
+    for (bit = 0; bit < 8; bit++) {
+      unsigned char new_val = old_val ^ (1 << bit);
+      stuff->perturbed[pos] = new_val;
+      if (test_decompress(stuff)) {
+        fprintf(
+            stderr,
+            "Flipping byte %zu bit %zu (0x%02x -> 0x%02x) "
+            "produced a successful decompression!\n",
+            pos, bit, old_val, new_val);
+      }
+    }
+    stuff->perturbed[pos] = old_val;
+  }
+  return 1;
+}
+
+static int perturb_bytes(stuff_t* stuff) {
+  size_t pos;
+  size_t new_val;
+  for (pos = 0; pos < stuff->input_size; pos++) {
+    unsigned char old_val = stuff->input[pos];
+    if (pos % 1000 == 0) {
+      fprintf(stderr, "Perturbing byte %zu / %zu\n", pos, stuff->input_size);
+    }
+    for (new_val = 0; new_val < 256; new_val++) {
+      stuff->perturbed[pos] = new_val;
+      if (test_decompress(stuff)) {
+        fprintf(
+            stderr,
+            "Changing byte %zu (0x%02x -> 0x%02x) "
+            "produced a successful decompression!\n",
+            pos, old_val, (unsigned char)new_val);
+      }
+    }
+    stuff->perturbed[pos] = old_val;
+  }
+  return 1;
+}
+
+int main(int argc, char* argv[]) {
+  stuff_t stuff;
+
+  if(!init_stuff(&stuff, argc, argv)) {
+    fprintf(stderr, "Failed to init.\n");
+    return 1;
+  }
+
+  if (test_decompress(&stuff)) {
+    fprintf(stderr, "Blob already decompresses successfully!\n");
+    return 1;
+  }
+
+  perturb_bits(&stuff);
+
+  perturb_bytes(&stuff);
+
+  print_summary(&stuff);
+
+  free_stuff(&stuff);
+
+  return 0;
+}