thodg/libgit2/src/revparse.c

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• Hash : 38533d5a
  Author :
  Date : 2012-04-27T14:11:12
  

  Implementing rev-parse's "ref~2" syntax. Also extended the test suite to include chaining operators, e.g. "master^2~3^4".

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• src/revparse.c

• /*
   * Copyright (C) 2009-2012 the libgit2 contributors
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  
  #include <assert.h>
  
  #include "common.h"
  #include "buffer.h"
  
  #include "git2/revparse.h"
  #include "git2/object.h"
  #include "git2/oid.h"
  #include "git2/refs.h"
  #include "git2/tag.h"
  #include "git2/commit.h"
  
  GIT_BEGIN_DECL
  
  typedef enum {
     REVPARSE_STATE_INIT,
     REVPARSE_STATE_CARET,
     REVPARSE_STATE_LINEAR,
     REVPARSE_STATE_DONE,
  } revparse_state;
  
  static void set_invalid_syntax_err(const char *spec)
  {
     giterr_set(GITERR_INVALID, "Refspec '%s' is not valid.", spec);
  }
  
  static int revparse_lookup_fully_qualifed_ref(git_object **out, git_repository *repo, const char*spec)
  {
     git_reference *ref;
     git_object *obj = NULL;
  
     if (!git_reference_lookup(&ref, repo, spec)) {
        git_reference *resolved_ref;
        if (!git_reference_resolve(&resolved_ref, ref)) {
           if (!git_object_lookup(&obj, repo, git_reference_oid(resolved_ref), GIT_OBJ_ANY)) {
              *out = obj;
           }
           git_reference_free(resolved_ref);
        }
        git_reference_free(ref);
     }
     if (obj) {
        return 0;
     }
  
     return GIT_ERROR;
  }
  
  static int revparse_lookup_object(git_object **out, git_repository *repo, const char *spec)
  {
     size_t speclen = strlen(spec);
     git_object *obj = NULL;
     git_oid oid;
     git_buf refnamebuf = GIT_BUF_INIT;
     static const char* formatters[] = {
        "refs/%s",
        "refs/tags/%s",
        "refs/heads/%s",
        "refs/remotes/%s",
        "refs/remotes/%s/HEAD",
        NULL
     };
     unsigned int i;
     const char *substr;
  
     /* "git describe" output; snip everything before/including "-g" */
     substr = strstr(spec, "-g");
     if (substr) {
        spec = substr + 2;
        speclen = strlen(spec);
     }
  
     /* SHA or prefix */
     if (!git_oid_fromstrn(&oid, spec, speclen)) {
        if (!git_object_lookup_prefix(&obj, repo, &oid, speclen, GIT_OBJ_ANY)) {
           *out = obj;
           return 0;
        }
     }
  
     /* Fully-named ref */
     if (!revparse_lookup_fully_qualifed_ref(&obj, repo, spec)) {
        *out = obj;
        return 0;
     }
  
     /* Partially-named ref; match in this order: */
     for (i=0; formatters[i]; i++) {
        git_buf_clear(&refnamebuf);
        if (git_buf_printf(&refnamebuf, formatters[i], spec) < 0) {
           return GIT_ERROR;
        }
  
        if (!revparse_lookup_fully_qualifed_ref(&obj, repo, git_buf_cstr(&refnamebuf))) {
           git_buf_free(&refnamebuf);
           *out = obj;
           return 0;
        }
     }
     git_buf_free(&refnamebuf);
  
     giterr_set(GITERR_REFERENCE, "Refspec '%s' not found.", spec);
     return GIT_ERROR;
  }
  
  
  static int walk_ref_history(git_object **out, const char *refspec, const char *reflogspec)
  {
     /* TODO */
  
     /* Empty refspec means current branch */
  
     /* Possible syntaxes for reflogspec:
      * "8" -> 8th prior value for the ref
      * "-2" -> nth branch checked out before the current one (refspec must be empty)
      * "yesterday", "1 month 2 weeks 3 days 4 hours 5 seconds ago", "1979-02-26 18:30:00"
      *   -> value of ref at given point in time
      * "upstream" or "u" -> branch the ref is set to build on top of
      * */
     return 0;
  }
  
  static git_object* dereference_object(git_object *obj)
  {
     git_otype type = git_object_type(obj);
     git_object *newobj = NULL;
     git_tree *tree = NULL;
  
     switch (type) {
     case GIT_OBJ_COMMIT:
        if (0 == git_commit_tree(&tree, (git_commit*)obj)) {
           return (git_object*)tree;
        }
        break;
     case GIT_OBJ_TAG:
        if (0 == git_tag_target(&newobj, (git_tag*)obj)) {
           return newobj;
        }
        break;
  
     default:
     case GIT_OBJ_TREE:
     case GIT_OBJ_BLOB:
     case GIT_OBJ_OFS_DELTA:
     case GIT_OBJ_REF_DELTA:
        break;
     }
  
     /* Can't dereference some types */
     return NULL;
  }
  
  static int dereference_to_type(git_object **out, git_object *obj, git_otype target_type)
  {
     git_object *obj1 = obj, *obj2 = obj;
  
     while (1) {
        git_otype this_type = git_object_type(obj1);
  
        if (this_type == target_type) {
           *out = obj1;
           return 0;
        }
  
        /* Dereference once, if possible. */
        obj2 = dereference_object(obj1);
        if (!obj2) {
           giterr_set(GITERR_REFERENCE, "Can't dereference to type");
           return GIT_ERROR;
        }
        if (obj1 != obj) {
           git_object_free(obj1);
        }
        obj1 = obj2;
     }
  }
  
  static git_otype parse_obj_type(const char *str)
  {
     if (!strcmp(str, "{commit}")) return GIT_OBJ_COMMIT;
     if (!strcmp(str, "{tree}")) return GIT_OBJ_TREE;
     if (!strcmp(str, "{blob}")) return GIT_OBJ_BLOB;
     if (!strcmp(str, "{tag}")) return GIT_OBJ_TAG;
     return GIT_OBJ_BAD;
  }
  
  static int handle_caret_syntax(git_object **out, git_object *obj, const char *movement)
  {
     git_commit *commit;
     int n;
  
     if (*movement == '{') {
        if (movement[strlen(movement)-1] != '}') {
           set_invalid_syntax_err(movement);
           return GIT_ERROR;
        }
  
        /* {} -> Dereference until we reach an object that isn't a tag. */
        if (strlen(movement) == 2) {
           git_object *newobj = obj;
           git_object *newobj2 = newobj;
           while (git_object_type(newobj2) == GIT_OBJ_TAG) {
              newobj2 = dereference_object(newobj);
              if (newobj != obj) git_object_free(newobj);
              if (!newobj2) {
                 giterr_set(GITERR_REFERENCE, "Couldn't find object of target type.");
                 return GIT_ERROR;
              }
              newobj = newobj2;
           }
           *out = newobj2;
           return 0;
        }
        
        /* {/...} -> Walk all commits until we see a commit msg that matches the phrase. */
        if (movement[1] == '/') {
           /* TODO */
           return GIT_ERROR;
        }
  
        /* {...} -> Dereference until we reach an object of a certain type. */
        if (dereference_to_type(out, obj, parse_obj_type(movement)) < 0) {
           return GIT_ERROR;
        }
        return 0;
     }
  
     /* Dereference until we reach a commit. */
     if (dereference_to_type(&obj, obj, GIT_OBJ_COMMIT) < 0) {
        /* Can't dereference to a commit; fail */
        return GIT_ERROR;
     }
  
     /* "^" is the same as "^1" */
     if (strlen(movement) == 0) {
        n = 1;
     } else {
        git__strtol32(&n, movement, NULL, 0);
     }
     commit = (git_commit*)obj;
  
     /* "^0" just returns the input */
     if (n == 0) {
        *out = obj;
        return 0;
     }
  
     if (git_commit_parent(&commit, commit, n-1) < 0) {
        return GIT_ERROR;
     }
  
     *out = (git_object*)commit;
     return 0;
  }
  
  static int handle_linear_syntax(git_object **out, git_object *obj, const char *movement)
  {
     git_commit *commit1, *commit2;
     int i, n;
  
     /* Dereference until we reach a commit. */
     if (dereference_to_type(&obj, obj, GIT_OBJ_COMMIT) < 0) {
        /* Can't dereference to a commit; fail */
        return GIT_ERROR;
     }
  
     /* "~" is the same as "~1" */
     if (strlen(movement) == 0) {
        n = 1;
     } else {
        git__strtol32(&n, movement, NULL, 0);
     }
     commit1 = (git_commit*)obj;
  
     /* "~0" just returns the input */
     if (n == 0) {
        *out = obj;
        return 0;
     }
  
     for (i=0; i<n; i++) {
        if (git_commit_parent(&commit2, commit1, 0) < 0) {
           return GIT_ERROR;
        }
        if (commit1 != (git_commit*)obj) {
           git_commit_free(commit1);
        }
        commit1 = commit2;
     }
  
     *out = (git_object*)commit1;
     return 0;
  }
  
  int git_revparse_single(git_object **out, git_repository *repo, const char *spec)
  {
     revparse_state current_state = REVPARSE_STATE_INIT;
     revparse_state next_state = REVPARSE_STATE_INIT;
     const char *spec_cur = spec;
     git_object *cur_obj = NULL;
     git_object *next_obj = NULL;
     git_buf specbuffer = GIT_BUF_INIT;
     git_buf stepbuffer = GIT_BUF_INIT;
     int keep_looping = 1;
     int retcode = 0;
  
     assert(out && repo && spec);
  
     while (keep_looping) {
        switch (current_state) {
        case REVPARSE_STATE_INIT:
           if (!*spec_cur) {
              /* No operators, just a name. Find it and return. */
              return revparse_lookup_object(out, repo, spec);
           } else if (*spec_cur == '@') {
              /* '@' syntax doesn't allow chaining */
              git_buf_puts(&stepbuffer, spec_cur);
              retcode = walk_ref_history(out, git_buf_cstr(&specbuffer), git_buf_cstr(&stepbuffer));
              next_state = REVPARSE_STATE_DONE;
           } else if (*spec_cur == '^') {
              next_state = REVPARSE_STATE_CARET;
           } else if (*spec_cur == '~') {
              next_state = REVPARSE_STATE_LINEAR;
           } else {
              git_buf_putc(&specbuffer, *spec_cur);
           }
           spec_cur++;
  
           if (current_state != next_state) {
              /* Leaving INIT state, find the object specified, in case that state needs it */
              retcode = revparse_lookup_object(&next_obj, repo, git_buf_cstr(&specbuffer));
              if (retcode < 0) {
                 next_state = REVPARSE_STATE_DONE;
              }
           }
           break;
  
  
        case REVPARSE_STATE_CARET:
           /* Gather characters until NULL, '~', or '^' */
           if (!*spec_cur) {
              retcode = handle_caret_syntax(out, cur_obj, git_buf_cstr(&stepbuffer));
              next_state = REVPARSE_STATE_DONE;
           } else if (*spec_cur == '~') {
              retcode = handle_caret_syntax(&next_obj, cur_obj, git_buf_cstr(&stepbuffer));
              git_buf_clear(&stepbuffer);
              next_state = !retcode ? REVPARSE_STATE_LINEAR : REVPARSE_STATE_DONE;
           } else if (*spec_cur == '^') {
              retcode = handle_caret_syntax(&next_obj, cur_obj, git_buf_cstr(&stepbuffer));
              git_buf_clear(&stepbuffer);
              if (retcode < 0) {
                 next_state = REVPARSE_STATE_DONE;
              }
           } else {
              git_buf_putc(&stepbuffer, *spec_cur);
           }
           spec_cur++;
           break;
  
        case REVPARSE_STATE_LINEAR:
           if (!*spec_cur) {
              retcode = handle_linear_syntax(out, cur_obj, git_buf_cstr(&stepbuffer));
              next_state = REVPARSE_STATE_DONE;
           } else if (*spec_cur == '~') {
              retcode = handle_linear_syntax(&next_obj, cur_obj, git_buf_cstr(&stepbuffer));
              git_buf_clear(&stepbuffer);
              if (retcode < 0) {
                 next_state = REVPARSE_STATE_DONE;
              }
           } else if (*spec_cur == '^') {
              retcode = handle_linear_syntax(&next_obj, cur_obj, git_buf_cstr(&stepbuffer));
              git_buf_clear(&stepbuffer);
              next_state = !retcode ? REVPARSE_STATE_CARET : REVPARSE_STATE_DONE;
           } else {
              git_buf_putc(&stepbuffer, *spec_cur);
           }
           spec_cur++;
           break;
  
        case REVPARSE_STATE_DONE:
           keep_looping = 0;
           break;
        }
  
        current_state = next_state;
        if (cur_obj != next_obj) {
           git_object_free(cur_obj);
           cur_obj = next_obj;
        }
     }
  
     git_buf_free(&specbuffer);
     git_buf_free(&stepbuffer);
     return retcode;
  }
  
  
  GIT_END_DECL
  

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