Refactorings for v1 extract, other refactorings

Previous implementation sent too many bytes to decompressor if size was
less than 1024.

CMakeLists.txt

@@ -83,6 +83,7 @@ add_executable(test_simplearchiver
     src/test.c
     src/parser.c
     src/helpers.c
+    src/archiver.c
     src/algorithms/linear_congruential_gen.c
     src/data_structures/linked_list.c
     src/data_structures/hash_map.c

file_format.md

@@ -118,8 +118,16 @@ Following the link-count bytes, the following bytes are added for each symlink:
     1. The first byte.
         1. The first bit is UNSET if relative links are preferred, and is SET if
            absolute links are preferred.
+        2. The second bit is "user read permission".
+        3. The third bit is "user write permission".
+        4. The fourth bit is "user execute permission".
+        5. The fifth bit is "group read permission".
+        6. The sixth bit is "group write permission".
+        7. The seventh bit is "group execute permission".
+        8. The eighth bit is "other read permission".
     2. The second byte.
-        1. Currently unused.
+        1. The first bit is "other write permission".
+        2. The second bit is "other execute permission".
 2. 2 bytes 16-bit unsigned integer "link name" in big-endian. This does not
    include the NULL at the end of the string. Must not be zero.
 3. X bytes of link-name (length defined by previous value). Is a NULL-terminated

src/archiver.c

@@ -767,46 +767,8 @@ int write_files_fn(void *data, void *ud) {
         // fprintf(stderr, "DEBUG: abs_path: %s\nDEBUG: link_abs_path: %s\n",
         //                 (char*)abs_path, (char*)link_abs_path);
 
-        // Compare paths to get relative path.
-        // Get first non-common char.
-        size_t idx;
-        size_t last_slash;
-        for (idx = 0, last_slash = 0;
-             idx < strlen(abs_path) && idx < strlen(link_abs_path); ++idx) {
-          if (((const char *)abs_path)[idx] !=
-              ((const char *)link_abs_path)[idx]) {
-            break;
-          } else if (((const char *)abs_path)[idx] == '/') {
-            last_slash = idx + 1;
-          }
-        }
-        // Get substrings of both paths.
-        char *link_substr = (char *)link_abs_path + last_slash;
-        char *dest_substr = (char *)abs_path + last_slash;
-        rel_path = malloc(strlen(dest_substr) + 1);
-        strncpy(rel_path, dest_substr, strlen(dest_substr) + 1);
-        // fprintf(stderr, "DEBUG: link_substr: %s\nDEBUG: dest_substr: %s\n",
-        //         link_substr, dest_substr);
-
-        // Generate the relative path.
-        int_fast8_t has_slash = 0;
-        idx = 0;
-        do {
-          for (; link_substr[idx] != '/' && link_substr[idx] != 0; ++idx);
-          if (link_substr[idx] == 0) {
-            has_slash = 0;
-          } else {
-            has_slash = 1;
-            char *new_rel_path = malloc(strlen(rel_path) + 1 + 3);
-            new_rel_path[0] = '.';
-            new_rel_path[1] = '.';
-            new_rel_path[2] = '/';
-            strncpy(new_rel_path + 3, rel_path, strlen(rel_path) + 1);
-            free(rel_path);
-            rel_path = new_rel_path;
-            ++idx;
-          }
-        } while (has_slash);
+        rel_path =
+            simple_archiver_filenames_to_relative_path(link_abs_path, abs_path);
       }
     }
 
@@ -1150,6 +1112,86 @@ void cleanup_internal_file_info(SDArchiverInternalFileInfo **file_info) {
 #if SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN || \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_MAC ||          \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_LINUX
+mode_t permissions_from_bits_v1_symlink(const uint8_t flags[2],
+                                        uint_fast8_t print) {
+  mode_t permissions = 0;
+
+  if ((flags[0] & 2) != 0) {
+    permissions |= S_IRUSR;
+    if (print) {
+      fprintf(stderr, "r");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+  if ((flags[0] & 4) != 0) {
+    permissions |= S_IWUSR;
+    if (print) {
+      fprintf(stderr, "w");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+  if ((flags[0] & 8) != 0) {
+    permissions |= S_IXUSR;
+    if (print) {
+      fprintf(stderr, "x");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+  if ((flags[0] & 0x10) != 0) {
+    permissions |= S_IRGRP;
+    if (print) {
+      fprintf(stderr, "r");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+  if ((flags[0] & 0x20) != 0) {
+    permissions |= S_IWGRP;
+    if (print) {
+      fprintf(stderr, "w");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+  if ((flags[0] & 0x40) != 0) {
+    permissions |= S_IXGRP;
+    if (print) {
+      fprintf(stderr, "x");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+  if ((flags[0] & 0x80) != 0) {
+    permissions |= S_IROTH;
+    if (print) {
+      fprintf(stderr, "r");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+  if ((flags[1] & 1) != 0) {
+    permissions |= S_IWOTH;
+    if (print) {
+      fprintf(stderr, "w");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+  if ((flags[1] & 2) != 0) {
+    permissions |= S_IXOTH;
+    if (print) {
+      fprintf(stderr, "x");
+    }
+  } else if (print) {
+    fprintf(stderr, "-");
+  }
+
+  return permissions;
+}
+
 mode_t permissions_from_bits_version_1(const uint8_t flags[4],
                                        uint_fast8_t print) {
   mode_t permissions = 0;
@@ -1229,6 +1271,55 @@ mode_t permissions_from_bits_version_1(const uint8_t flags[4],
 
   return permissions;
 }
+
+void print_permissions(mode_t permissions) {
+  if ((permissions & S_IRUSR)) {
+    fprintf(stderr, "r");
+  } else {
+    fprintf(stderr, "-");
+  }
+  if ((permissions & S_IWUSR)) {
+    fprintf(stderr, "w");
+  } else {
+    fprintf(stderr, "-");
+  }
+  if ((permissions & S_IXUSR)) {
+    fprintf(stderr, "x");
+  } else {
+    fprintf(stderr, "-");
+  }
+  if ((permissions & S_IRGRP)) {
+    fprintf(stderr, "r");
+  } else {
+    fprintf(stderr, "-");
+  }
+  if ((permissions & S_IWGRP)) {
+    fprintf(stderr, "w");
+  } else {
+    fprintf(stderr, "-");
+  }
+  if ((permissions & S_IXGRP)) {
+    fprintf(stderr, "x");
+  } else {
+    fprintf(stderr, "-");
+  }
+  if ((permissions & S_IROTH)) {
+    fprintf(stderr, "r");
+  } else {
+    fprintf(stderr, "-");
+  }
+  if ((permissions & S_IWOTH)) {
+    fprintf(stderr, "w");
+  } else {
+    fprintf(stderr, "-");
+  }
+  if ((permissions & S_IXOTH)) {
+    fprintf(stderr, "x");
+  } else {
+    fprintf(stderr, "-");
+  }
+}
+
 #endif
 
 void simple_archiver_internal_cleanup_int_fd(int *fd) {
@@ -1489,6 +1580,18 @@ int simple_archiver_write_v0(FILE *out_f, SDArchiverState *state,
 
 int simple_archiver_write_v1(FILE *out_f, SDArchiverState *state,
                              const SDArchiverLinkedList *filenames) {
+  // First create a "set" of absolute paths to given filenames.
+  __attribute__((cleanup(simple_archiver_hash_map_free)))
+  SDArchiverHashMap *abs_filenames = simple_archiver_hash_map_init();
+  void **ptr_array = malloc(sizeof(void *) * 2);
+  ptr_array[0] = abs_filenames;
+  ptr_array[1] = (void *)state->parsed->user_cwd;
+  if (simple_archiver_list_get(filenames, filenames_to_abs_map_fn, ptr_array)) {
+    free(ptr_array);
+    return SDAS_FAILED_TO_CREATE_MAP;
+  }
+  free(ptr_array);
+
   // TODO Impl.
   fprintf(stderr, "Writing v1 unimplemented\n");
   return SDAS_INTERNAL_ERROR;
@@ -1666,6 +1769,17 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
           }
         } else {
           skip = 0;
+          int fd = open((const char *)buf, O_RDONLY | O_NOFOLLOW);
+          if (fd == -1) {
+            if (errno == ELOOP) {
+              // Is an existing symbolic file.
+              unlink((const char *)buf);
+            }
+          } else {
+            close(fd);
+            // Is an existing file.
+            unlink((const char *)buf);
+          }
         }
         if (!skip) {
           out_f_name = malloc(strlen((const char *)buf) + 1);
@@ -1675,17 +1789,17 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
     } else {
       __attribute__((
           cleanup(simple_archiver_helper_cleanup_malloced))) void *heap_buf =
-          malloc(u16 + 1);
+          malloc((uint32_t)u16 + 1);
       uint8_t *uc_heap_buf = heap_buf;
-      if (fread(uc_heap_buf, 1, u16 + 1, in_f) != (size_t)u16 + 1) {
+      if (fread(uc_heap_buf, 1, (uint32_t)u16 + 1, in_f) != (size_t)u16 + 1) {
         return SDAS_INVALID_FILE;
       }
-      uc_heap_buf[u16 - 1] = 0;
+      uc_heap_buf[u16] = 0;
       fprintf(stderr, "  Filename: %s\n", uc_heap_buf);
       if (do_extract) {
         if ((state->parsed->flags & 0x8) == 0) {
           __attribute__((cleanup(simple_archiver_helper_cleanup_FILE)))
-          FILE *test_fd = fopen((const char *)buf, "rb");
+          FILE *test_fd = fopen((const char *)uc_heap_buf, "rb");
           if (test_fd) {
             skip = 1;
             fprintf(stderr,
@@ -1696,10 +1810,22 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
           }
         } else {
           skip = 0;
+          int fd = open((const char *)uc_heap_buf, O_RDONLY | O_NOFOLLOW);
+          if (fd == -1) {
+            if (errno == ELOOP) {
+              // Is an existing symbolic file.
+              unlink((const char *)uc_heap_buf);
+            }
+          } else {
+            close(fd);
+            // Is an existing file.
+            unlink((const char *)uc_heap_buf);
+          }
         }
         if (!skip) {
-          out_f_name = malloc(strlen((const char *)buf) + 1);
-          memcpy(out_f_name, buf, strlen((const char *)buf) + 1);
+          out_f_name = malloc(strlen((const char *)uc_heap_buf) + 1);
+          memcpy(out_f_name, uc_heap_buf,
+                 strlen((const char *)uc_heap_buf) + 1);
         }
       }
     }
@@ -1822,6 +1948,12 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
 
         simple_archiver_helper_make_dirs((const char *)out_f_name);
         out_f = fopen(out_f_name, "wb");
+        if (!out_f) {
+          fprintf(stderr,
+                  "WARNING: Failed to open \"%s\" for writing! (No write "
+                  "permissions?)\n",
+                  (char *)out_f_name);
+        }
         __attribute__((
             cleanup(cleanup_temp_filename_delete))) void **ptrs_array =
             malloc(sizeof(void *) * 2);
@@ -1830,7 +1962,7 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
 #if SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN || \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_MAC ||          \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_LINUX
-        if (is_compressed) {
+        if (is_compressed && out_f) {
           // Handle SIGPIPE.
           signal(SIGPIPE, handle_sig_pipe);
 
@@ -2038,10 +2170,12 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
                 // Error.
                 return SDAS_INTERNAL_ERROR;
               }
-              fwrite(buf, 1, fread_ret, out_f);
-              if (ferror(out_f)) {
-                // Error.
-                return SDAS_INTERNAL_ERROR;
+              if (out_f) {
+                fwrite(buf, 1, fread_ret, out_f);
+                if (ferror(out_f)) {
+                  // Error.
+                  return SDAS_INTERNAL_ERROR;
+                }
               }
               compressed_file_size -= fread_ret;
             } else {
@@ -2050,10 +2184,12 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
                 // Error.
                 return SDAS_INTERNAL_ERROR;
               }
-              fwrite(buf, 1, fread_ret, out_f);
-              if (ferror(out_f)) {
-                // Error.
-                return SDAS_INTERNAL_ERROR;
+              if (out_f) {
+                fwrite(buf, 1, fread_ret, out_f);
+                if (ferror(out_f)) {
+                  // Error.
+                  return SDAS_INTERNAL_ERROR;
+                }
               }
               compressed_file_size -= fread_ret;
             }
@@ -2066,7 +2202,9 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
         }
 
         ptrs_array[0] = NULL;
-        fprintf(stderr, "  Extracted.\n");
+        if (out_f) {
+          fprintf(stderr, "  Extracted.\n");
+        }
 #endif
       } else {
         while (u64 != 0) {
@@ -2145,26 +2283,108 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
         fprintf(stderr, "  Link relative path: %s\n", (char *)rel_path);
       }
 
-      if (do_extract) {
+      if (do_extract && !skip) {
         simple_archiver_helper_make_dirs((const char *)out_f_name);
         if (abs_path && rel_path) {
           if (abs_preferred) {
 #if SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN || \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_MAC ||          \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_LINUX
-            int ret = symlink(abs_path, out_f_name);
+            int_fast8_t retry_symlink = 0;
+            int ret;
+          V0_SYMLINK_CREATE_RETRY_0:
+            ret = symlink(abs_path, out_f_name);
             if (ret == -1) {
-              return SDAS_FAILED_TO_EXTRACT_SYMLINK;
+              if (retry_symlink) {
+                fprintf(stderr,
+                        "WARNING: Failed to create symlink after removing "
+                        "existing symlink!\n");
+                goto V0_SYMLINK_CREATE_AFTER_0;
+              } else if (errno == EEXIST) {
+                if ((state->parsed->flags & 8) == 0) {
+                  fprintf(
+                      stderr,
+                      "WARNING: Symlink already exists and "
+                      "\"--overwrite-extract\" is not specified, skipping!\n");
+                  goto V0_SYMLINK_CREATE_AFTER_0;
+                } else {
+                  fprintf(stderr,
+                          "NOTICE: Symlink already exists and "
+                          "\"--overwrite-extract\" specified, attempting to "
+                          "overwrite...\n");
+                  unlink(out_f_name);
+                  retry_symlink = 1;
+                  goto V0_SYMLINK_CREATE_RETRY_0;
+                }
+              } else {
+                return SDAS_FAILED_TO_EXTRACT_SYMLINK;
+              }
             }
+            ret = fchmodat(AT_FDCWD, out_f_name, permissions,
+                           AT_SYMLINK_NOFOLLOW);
+            if (ret == -1) {
+              if (errno == EOPNOTSUPP) {
+                fprintf(stderr,
+                        "NOTICE: Setting permissions of symlink is not "
+                        "supported by FS/OS!\n");
+              } else {
+                fprintf(stderr,
+                        "WARNING: Failed to set permissions of symlink (%d)!\n",
+                        errno);
+              }
+            }
+          V0_SYMLINK_CREATE_AFTER_0:
+            retry_symlink = 1;
 #endif
           } else {
 #if SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN || \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_MAC ||          \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_LINUX
-            int ret = symlink(rel_path, out_f_name);
+            int_fast8_t retry_symlink = 0;
+            int ret;
+          V0_SYMLINK_CREATE_RETRY_1:
+            ret = symlink(rel_path, out_f_name);
             if (ret == -1) {
-              return SDAS_FAILED_TO_EXTRACT_SYMLINK;
+              if (retry_symlink) {
+                fprintf(stderr,
+                        "WARNING: Failed to create symlink after removing "
+                        "existing symlink!\n");
+                goto V0_SYMLINK_CREATE_AFTER_1;
+              } else if (errno == EEXIST) {
+                if ((state->parsed->flags & 8) == 0) {
+                  fprintf(
+                      stderr,
+                      "WARNING: Symlink already exists and "
+                      "\"--overwrite-extract\" is not specified, skipping!\n");
+                  goto V0_SYMLINK_CREATE_AFTER_1;
+                } else {
+                  fprintf(stderr,
+                          "NOTICE: Symlink already exists and "
+                          "\"--overwrite-extract\" specified, attempting to "
+                          "overwrite...\n");
+                  unlink(out_f_name);
+                  retry_symlink = 1;
+                  goto V0_SYMLINK_CREATE_RETRY_1;
+                }
+              } else {
+                return SDAS_FAILED_TO_EXTRACT_SYMLINK;
+              }
             }
+            ret = fchmodat(AT_FDCWD, out_f_name, permissions,
+                           AT_SYMLINK_NOFOLLOW);
+            if (ret == -1) {
+              if (errno == EOPNOTSUPP) {
+                fprintf(stderr,
+                        "NOTICE: Setting permissions of symlink is not "
+                        "supported by FS/OS!\n");
+              } else {
+                fprintf(stderr,
+                        "WARNING: Failed to set permissions of symlink (%d)!\n",
+                        errno);
+              }
+            }
+          V0_SYMLINK_CREATE_AFTER_1:
+            retry_symlink = 1;
 #endif
           }
         } else if (abs_path) {
@@ -2175,6 +2395,19 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
           if (ret == -1) {
             return SDAS_FAILED_TO_EXTRACT_SYMLINK;
           }
+          ret =
+              fchmodat(AT_FDCWD, out_f_name, permissions, AT_SYMLINK_NOFOLLOW);
+          if (ret == -1) {
+            if (errno == EOPNOTSUPP) {
+              fprintf(stderr,
+                      "NOTICE: Setting permissions of symlink is not supported "
+                      "by FS/OS!\n");
+            } else {
+              fprintf(stderr,
+                      "WARNING: Failed to set permissions of symlink (%d)!\n",
+                      errno);
+            }
+          }
 #endif
         } else if (rel_path) {
 #if SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN || \
@@ -2184,6 +2417,19 @@ int simple_archiver_parse_archive_version_0(FILE *in_f, int_fast8_t do_extract,
           if (ret == -1) {
             return SDAS_FAILED_TO_EXTRACT_SYMLINK;
           }
+          ret =
+              fchmodat(AT_FDCWD, out_f_name, permissions, AT_SYMLINK_NOFOLLOW);
+          if (ret == -1) {
+            if (errno == EOPNOTSUPP) {
+              fprintf(stderr,
+                      "NOTICE: Setting permissions of symlink is not supported "
+                      "by FS/OS!\n");
+            } else {
+              fprintf(stderr,
+                      "WARNING: Failed to set permissions of symlink (%d)!\n",
+                      errno);
+            }
+          }
 #endif
         } else {
           fprintf(
@@ -2291,6 +2537,13 @@ int simple_archiver_parse_archive_version_1(FILE *in_f, int_fast8_t do_extract,
       return SDAS_INVALID_FILE;
     }
     const uint_fast8_t absolute_preferred = (buf[0] & 1) ? 1 : 0;
+
+#if SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN || \
+    SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_MAC ||          \
+    SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_LINUX
+    mode_t permissions = permissions_from_bits_v1_symlink(buf, 0);
+#endif
+
     uint_fast8_t link_extracted = 0;
     uint_fast8_t skip_due_to_map = 0;
 
@@ -2312,6 +2565,13 @@ int simple_archiver_parse_archive_version_1(FILE *in_f, int_fast8_t do_extract,
 
     if (!do_extract) {
       fprintf(stderr, "  Link name: %s\n", link_name);
+#if SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN || \
+    SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_MAC ||          \
+    SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_LINUX
+      fprintf(stderr, "  Link Permissions: ");
+      print_permissions(permissions);
+      fprintf(stderr, "\n");
+#endif
     }
 
     if (working_files_map &&
@@ -2340,12 +2600,49 @@ int simple_archiver_parse_archive_version_1(FILE *in_f, int_fast8_t do_extract,
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_MAC ||          \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_LINUX
         simple_archiver_helper_make_dirs(link_name);
+        int_fast8_t link_create_retry = 0;
+      V1_SYMLINK_CREATE_RETRY_0:
         ret = symlink(path, link_name);
         if (ret == -1) {
+          if (link_create_retry) {
+            fprintf(stderr,
+                    "WARNING: Failed to create symlink after removing existing "
+                    "symlink!\n");
+            goto V1_SYMLINK_CREATE_AFTER_0;
+          } else if (errno == EEXIST) {
+            if ((state->parsed->flags & 8) == 0) {
+              fprintf(stderr,
+                      "WARNING: Symlink already exists and "
+                      "\"--overwrite-extract\" is not specified, skipping!\n");
+              goto V1_SYMLINK_CREATE_AFTER_0;
+            } else {
+              fprintf(
+                  stderr,
+                  "NOTICE: Symlink already exists and \"--overwrite-extract\" "
+                  "specified, attempting to overwrite...\n");
+              unlink(link_name);
+              link_create_retry = 1;
+              goto V1_SYMLINK_CREATE_RETRY_0;
+            }
+          }
           return SDAS_FAILED_TO_EXTRACT_SYMLINK;
         }
+        ret = fchmodat(AT_FDCWD, link_name, permissions, AT_SYMLINK_NOFOLLOW);
+        if (ret == -1) {
+          if (errno == EOPNOTSUPP) {
+            fprintf(stderr,
+                    "NOTICE: Setting permissions of symlink is not supported "
+                    "by FS/OS!\n");
+          } else {
+            fprintf(stderr,
+                    "WARNING: Failed to set permissions of symlink (%d)!\n",
+                    errno);
+          }
+        }
         link_extracted = 1;
         fprintf(stderr, "  %s -> %s\n", link_name, path);
+      V1_SYMLINK_CREATE_AFTER_0:
+        link_create_retry = 1;
 #endif
       } else {
         fprintf(stderr, "  Abs path: %s\n", path);
@@ -2373,12 +2670,49 @@ int simple_archiver_parse_archive_version_1(FILE *in_f, int_fast8_t do_extract,
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_MAC ||          \
     SIMPLE_ARCHIVER_PLATFORM == SIMPLE_ARCHIVER_PLATFORM_LINUX
         simple_archiver_helper_make_dirs(link_name);
+        int_fast8_t link_create_retry = 0;
+      V1_SYMLINK_CREATE_RETRY_1:
         ret = symlink(path, link_name);
         if (ret == -1) {
+          if (link_create_retry) {
+            fprintf(stderr,
+                    "WARNING: Failed to create symlink after removing existing "
+                    "symlink!\n");
+            goto V1_SYMLINK_CREATE_AFTER_1;
+          } else if (errno == EEXIST) {
+            if ((state->parsed->flags & 8) == 0) {
+              fprintf(stderr,
+                      "WARNING: Symlink already exists and "
+                      "\"--overwrite-extract\" is not specified, skipping!\n");
+              goto V1_SYMLINK_CREATE_AFTER_1;
+            } else {
+              fprintf(
+                  stderr,
+                  "NOTICE: Symlink already exists and \"--overwrite-extract\" "
+                  "specified, attempting to overwrite...\n");
+              unlink(link_name);
+              link_create_retry = 1;
+              goto V1_SYMLINK_CREATE_RETRY_1;
+            }
+          }
           return SDAS_FAILED_TO_EXTRACT_SYMLINK;
         }
+        ret = fchmodat(AT_FDCWD, link_name, permissions, AT_SYMLINK_NOFOLLOW);
+        if (ret == -1) {
+          if (errno == EOPNOTSUPP) {
+            fprintf(stderr,
+                    "NOTICE: Setting permissions of symlink is not supported "
+                    "by FS/OS!\n");
+          } else {
+            fprintf(stderr,
+                    "WARNING: Failed to set permissions of symlink (%d)!\n",
+                    errno);
+          }
+        }
         link_extracted = 1;
         fprintf(stderr, "  %s -> %s\n", link_name, path);
+      V1_SYMLINK_CREATE_AFTER_1:
+        link_create_retry = 1;
 #endif
       } else {
         fprintf(stderr, "  Rel path: %s\n", path);
@@ -2434,6 +2768,27 @@ int simple_archiver_parse_archive_version_1(FILE *in_f, int_fast8_t do_extract,
       }
       file_info->filename[u16] = 0;
 
+      if (state && state->parsed && (state->parsed->flags & 8) != 0) {
+        int fd = open((const char *)buf, O_RDONLY | O_NOFOLLOW);
+        if (fd == -1) {
+          if (errno == ELOOP) {
+            // Exists as a symlink.
+            fprintf(stderr,
+                    "WARNING: Filename \"%s\" already exists as symlink, "
+                    "removing...\n",
+                    (const char *)buf);
+            unlink((const char *)buf);
+          } else {
+            // File doesn't exist, do nothing.
+          }
+        } else {
+          close(fd);
+          fprintf(stderr, "WARNING: File \"%s\" already exists, removing...\n",
+                  (const char *)buf);
+          unlink((const char *)buf);
+        }
+      }
+
       if (fread(file_info->bit_flags, 1, 4, in_f) != 4) {
         return SDAS_INVALID_FILE;
       }
@@ -2872,3 +3227,53 @@ int simple_archiver_de_compress(int pipe_fd_in[2], int pipe_fd_out[2],
   return 1;
 #endif
 }
+
+char *simple_archiver_filenames_to_relative_path(const char *from_abs,
+                                                 const char *to_abs) {
+  if (!from_abs || !to_abs) {
+    return NULL;
+  }
+
+  // Get first non-common char and last slash before it.
+  uint_fast32_t idx;
+  uint_fast32_t last_slash;
+  for (idx = 0, last_slash = 0; idx < strlen(from_abs) && idx < strlen(to_abs);
+       ++idx) {
+    if (((const char *)to_abs)[idx] != ((const char *)from_abs)[idx]) {
+      break;
+    } else if (((const char *)to_abs)[idx] == '/') {
+      last_slash = idx + 1;
+    }
+  }
+
+  // Get substrings of both paths.
+  char *link_substr = (char *)from_abs + last_slash;
+  char *dest_substr = (char *)to_abs + last_slash;
+  char *rel_path = malloc(strlen(dest_substr) + 1);
+  strncpy(rel_path, dest_substr, strlen(dest_substr) + 1);
+
+  // fprintf(stderr, "DEBUG: link_substr \"%s\", dest_substr \"%s\"\n",
+  //     link_substr, dest_substr);
+
+  // Get the relative path finally.
+  int_fast8_t has_slash = 0;
+  idx = 0;
+  do {
+    for (; link_substr[idx] != '/' && link_substr[idx] != 0; ++idx);
+    if (link_substr[idx] == 0) {
+      has_slash = 0;
+    } else {
+      has_slash = 1;
+      char *new_rel_path = malloc(strlen(rel_path) + 1 + 3);
+      new_rel_path[0] = '.';
+      new_rel_path[1] = '.';
+      new_rel_path[2] = '/';
+      strncpy(new_rel_path + 3, rel_path, strlen(rel_path) + 1);
+      free(rel_path);
+      rel_path = new_rel_path;
+      ++idx;
+    }
+  } while (has_slash);
+
+  return rel_path;
+}

src/archiver.h

@@ -40,7 +40,7 @@ typedef struct SDArchiverState {
   size_t digits;
 } SDArchiverState;
 
-enum SDArchiverStateReturns {
+typedef enum SDArchiverStateReturns {
   SDAS_SUCCESS = 0,
   SDAS_HEADER_ALREADY_WRITTEN = 1,
   SDAS_FAILED_TO_WRITE,
@@ -53,7 +53,7 @@ enum SDArchiverStateReturns {
   SDAS_FAILED_TO_EXTRACT_SYMLINK,
   SDAS_FAILED_TO_CHANGE_CWD,
   SDAS_INVALID_WRITE_VERSION
-};
+} SDArchiverStateReturns;
 
 /// Returned pointer must not be freed.
 char *simple_archiver_error_to_string(enum SDArchiverStateReturns error);
@@ -88,4 +88,8 @@ int simple_archiver_parse_archive_version_1(FILE *in_f, int_fast8_t do_extract,
 int simple_archiver_de_compress(int pipe_fd_in[2], int pipe_fd_out[2],
                                 const char *cmd, void *pid_out);
 
+/// If returns non-NULL, must be free'd.
+char *simple_archiver_filenames_to_relative_path(const char *from_abs,
+                                                 const char *to_abs);
+
 #endif

src/main.c

@@ -97,7 +97,8 @@ int main(int argc, const char **argv) {
       int ret = simple_archiver_write_all(file, state, filenames);
       if (ret != SDAS_SUCCESS) {
         fprintf(stderr, "Error during writing.\n");
-        char *error_str = simple_archiver_error_to_string(ret);
+        char *error_str =
+            simple_archiver_error_to_string((SDArchiverStateReturns)ret);
         fprintf(stderr, "  %s\n", error_str);
       }
       fclose(file);
@@ -113,7 +114,8 @@ int main(int argc, const char **argv) {
       int ret = simple_archiver_write_all(stdout, state, filenames);
       if (ret != SDAS_SUCCESS) {
         fprintf(stderr, "Error during writing.\n");
-        char *error_str = simple_archiver_error_to_string(ret);
+        char *error_str =
+            simple_archiver_error_to_string((SDArchiverStateReturns)ret);
         fprintf(stderr, "  %s\n", error_str);
       }
     }
@@ -130,7 +132,8 @@ int main(int argc, const char **argv) {
       int ret = simple_archiver_parse_archive_info(file, 0, NULL);
       if (ret != 0) {
         fprintf(stderr, "Error during archive checking/examining.\n");
-        char *error_str = simple_archiver_error_to_string(ret);
+        char *error_str =
+            simple_archiver_error_to_string((SDArchiverStateReturns)ret);
         fprintf(stderr, "  %s\n", error_str);
       }
       fclose(file);
@@ -138,7 +141,8 @@ int main(int argc, const char **argv) {
       int ret = simple_archiver_parse_archive_info(stdin, 0, NULL);
       if (ret != 0) {
         fprintf(stderr, "Error during archive checking/examining.\n");
-        char *error_str = simple_archiver_error_to_string(ret);
+        char *error_str =
+            simple_archiver_error_to_string((SDArchiverStateReturns)ret);
         fprintf(stderr, "  %s\n", error_str);
       }
     }
@@ -157,7 +161,8 @@ int main(int argc, const char **argv) {
       int ret = simple_archiver_parse_archive_info(file, 1, state);
       if (ret != SDAS_SUCCESS) {
         fprintf(stderr, "Error during archive extracting.\n");
-        char *error_str = simple_archiver_error_to_string(ret);
+        char *error_str =
+            simple_archiver_error_to_string((SDArchiverStateReturns)ret);
         fprintf(stderr, "  %s\n", error_str);
       }
       fclose(file);
@@ -165,7 +170,8 @@ int main(int argc, const char **argv) {
       int ret = simple_archiver_parse_archive_info(stdin, 1, state);
       if (ret != SDAS_SUCCESS) {
         fprintf(stderr, "Error during archive extracting.\n");
-        char *error_str = simple_archiver_error_to_string(ret);
+        char *error_str =
+            simple_archiver_error_to_string((SDArchiverStateReturns)ret);
         fprintf(stderr, "  %s\n", error_str);
       }
     }

src/test.c

@@ -23,6 +23,7 @@
 #include <string.h>
 
 // Local includes.
+#include "archiver.h"
 #include "helpers.h"
 #include "parser_internal.h"
 
@@ -241,6 +242,21 @@ int main(void) {
     free(out);
   }
 
+  // Test archiver.
+  {
+    __attribute__((
+        cleanup(simple_archiver_helper_cleanup_c_string))) char *rel_path =
+        simple_archiver_filenames_to_relative_path(
+            "/one/two/three/four/five", "/one/two/branch/other/path");
+    CHECK_STREQ(rel_path, "../../branch/other/path");
+    simple_archiver_helper_cleanup_c_string(&rel_path);
+
+    rel_path = simple_archiver_filenames_to_relative_path(
+        "/one/two/three/four/five", "/one/two/three/other/dir/");
+    CHECK_STREQ(rel_path, "../other/dir/");
+    simple_archiver_helper_cleanup_c_string(&rel_path);
+  }
+
   printf("Checks checked: %u\n", checks_checked);
   printf("Checks passed:  %u\n", checks_passed);
   return checks_passed == checks_checked ? 0 : 1;