thodg/got/lib/diff_main.c

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• Hash : 336075a4
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  Date : 2022-06-25T09:22:02
  

  build with -Wmissing-prototypes ok stsp@

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• lib/diff_main.c

• /* Generic infrastructure to implement various diff algorithms (implementation). */
  /*
   * Copyright (c) 2020 Neels Hofmeyr <neels@hofmeyr.de>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  
  #include <sys/queue.h>
  #include <ctype.h>
  #include <errno.h>
  #include <stdint.h>
  #include <stdlib.h>
  #include <stdbool.h>
  #include <stdio.h>
  #include <string.h>
  #include <limits.h>
  #include <unistd.h>
  
  #include <assert.h>
  
  #include <arraylist.h>
  #include <diff_main.h>
  
  #include "diff_internal.h"
  #include "diff_debug.h"
  
  static int
  read_at(FILE *f, off_t at_pos, unsigned char *buf, size_t len)
  {
  	int r;
  	if (fseeko(f, at_pos, SEEK_SET) == -1)
  		return errno;
  	r = fread(buf, sizeof(char), len, f);
  	if ((r == 0 || r < len) && ferror(f))
  		return errno;
  	if (r != len)
  		return EIO;
  	return 0;
  }
  
  static int
  buf_cmp(const unsigned char *left, size_t left_len,
  	const unsigned char *right, size_t right_len,
  	bool ignore_whitespace)
  {
  	int cmp;
  
  	if (ignore_whitespace) {
  		int il = 0, ir = 0;
  		while (il < left_len && ir < right_len) {
  			unsigned char cl = left[il];
  			unsigned char cr = right[ir];
  
  			if (isspace(cl) && il < left_len) {
  				il++;
  				continue;
  			}
  			if (isspace(cr) && ir < right_len) {
  				ir++;
  				continue;
  			}
  
  			if (cl > cr)
  				return 1;
  			if (cr > cl)
  				return -1;
  			il++;
  			ir++;
  		}
  		while (il < left_len) {
  			unsigned char cl = left[il++];
  			if (!isspace(cl))
  				return 1;
  		}
  		while (ir < right_len) {
  			unsigned char cr = right[ir++];
  			if (!isspace(cr))
  				return -1;
  		}
  
  		return 0;
  	}
  
  	cmp = memcmp(left, right, MIN(left_len, right_len));
  	if (cmp)
  		return cmp;
  	if (left_len == right_len)
  		return 0;
  	return (left_len > right_len) ? 1 : -1;
  }
  
  int
  diff_atom_cmp(int *cmp,
  	      const struct diff_atom *left,
  	      const struct diff_atom *right)
  {
  	off_t remain_left, remain_right;
  	int flags = (left->root->diff_flags | right->root->diff_flags);
  	bool ignore_whitespace = (flags & DIFF_FLAG_IGNORE_WHITESPACE);
  
  	if (!left->len && !right->len) {
  		*cmp = 0;
  		return 0;
  	}
  	if (!ignore_whitespace) {
  		if (!right->len) {
  			*cmp = 1;
  			return 0;
  		}
  		if (!left->len) {
  			*cmp = -1;
  			return 0;
  		}
  	}
  
  	if (left->at != NULL && right->at != NULL) {
  		*cmp = buf_cmp(left->at, left->len, right->at, right->len,
  		    ignore_whitespace);
  		return 0;
  	}
  
  	remain_left = left->len;
  	remain_right = right->len;
  	while (remain_left > 0 || remain_right > 0) {
  		const size_t chunksz = 8192;
  		unsigned char buf_left[chunksz], buf_right[chunksz];
  		const uint8_t *p_left, *p_right;
  		off_t n_left, n_right;
  		ssize_t r;
  
  		if (!remain_right) {
  			*cmp = 1;
  			return 0;
  		}
  		if (!remain_left) {
  			*cmp = -1;
  			return 0;
  		}
  
  		n_left = MIN(chunksz, remain_left);
  		n_right = MIN(chunksz, remain_right);
  
  		if (left->at == NULL) {
  			r = read_at(left->root->f,
  				    left->pos + (left->len - remain_left),
  				    buf_left, n_left);
  			if (r) {
  				*cmp = 0;
  				return r;
  			}
  			p_left = buf_left;
  		} else {
  			p_left = left->at + (left->len - remain_left);
  		}
  
  		if (right->at == NULL) {
  			r = read_at(right->root->f,
  				    right->pos + (right->len - remain_right),
  				    buf_right, n_right);
  			if (r) {
  				*cmp = 0;
  				return r;
  			}
  			p_right = buf_right;
  		} else {
  			p_right = right->at + (right->len - remain_right);
  		}
  
  		r = buf_cmp(p_left, n_left, p_right, n_right,
  		    ignore_whitespace);
  		if (r) {
  			*cmp = r;
  			return 0;
  		}
  
  		remain_left -= n_left;
  		remain_right -= n_right;
  	}
  
  	*cmp = 0;
  	return 0;
  }
  
  int
  diff_atom_same(bool *same,
  	       const struct diff_atom *left,
  	       const struct diff_atom *right)
  {
  	int cmp;
  	int r;
  	if (left->hash != right->hash) {
  		*same = false;
  		return 0;
  	}
  	r = diff_atom_cmp(&cmp, left, right);
  	if (r) {
  		*same = true;
  		return r;
  	}
  	*same = (cmp == 0);
  	return 0;
  }
  
  static struct diff_chunk *
  diff_state_add_solved_chunk(struct diff_state *state,
  			    const struct diff_chunk *chunk)
  {
  	diff_chunk_arraylist_t *result;
  	struct diff_chunk *new_chunk;
  	enum diff_chunk_type last_t;
  	enum diff_chunk_type new_t;
  	struct diff_chunk *last;
  
  	/* Append to solved chunks; make sure that adjacent chunks of same type are combined, and that a minus chunk
  	 * never directly follows a plus chunk. */
  	result = &state->result->chunks;
  
  	last_t = result->len ? diff_chunk_type(&result->head[result->len - 1])
  		: CHUNK_EMPTY;
  	new_t = diff_chunk_type(chunk);
  
  	debug("ADD %s chunk #%u:\n", chunk->solved ? "solved" : "UNSOLVED",
  	      result->len);
  	debug("L\n");
  	debug_dump_atoms(&state->left, chunk->left_start, chunk->left_count);
  	debug("R\n");
  	debug_dump_atoms(&state->right, chunk->right_start, chunk->right_count);
  
  	if (result->len) {
  		last = &result->head[result->len - 1];
  		assert(chunk->left_start
  		       == last->left_start + last->left_count);
  		assert(chunk->right_start
  		       == last->right_start + last->right_count);
  	}
  
  	if (new_t == last_t) {
  		new_chunk = &result->head[result->len - 1];
  		new_chunk->left_count += chunk->left_count;
  		new_chunk->right_count += chunk->right_count;
  		debug("  - added chunk touches previous one of same type, joined:\n");
  		debug("L\n");
  		debug_dump_atoms(&state->left, new_chunk->left_start, new_chunk->left_count);
  		debug("R\n");
  		debug_dump_atoms(&state->right, new_chunk->right_start, new_chunk->right_count);
  	} else if (last_t == CHUNK_PLUS && new_t == CHUNK_MINUS) {
  		enum diff_chunk_type prev_last_t =
  			result->len > 1 ?
  				diff_chunk_type(&result->head[result->len - 2])
  				: CHUNK_EMPTY;
  		/* If a minus-chunk follows a plus-chunk, place it above the plus-chunk->
  		 * Is the one before that also a minus? combine. */
  		if (prev_last_t == CHUNK_MINUS) {
  			new_chunk = &result->head[result->len - 2];
  			new_chunk->left_count += chunk->left_count;
  			new_chunk->right_count += chunk->right_count;
  
  			debug("  - added minus-chunk follows plus-chunk,"
  			      " put before that plus-chunk and joined"
  			      " with preceding minus-chunk:\n");
  			debug("L\n");
  			debug_dump_atoms(&state->left, new_chunk->left_start, new_chunk->left_count);
  			debug("R\n");
  			debug_dump_atoms(&state->right, new_chunk->right_start, new_chunk->right_count);
  		} else {
  			ARRAYLIST_INSERT(new_chunk, *result, result->len - 1);
  			if (!new_chunk)
  				return NULL;
  			*new_chunk = *chunk;
  
  			/* The new minus chunk indicates to which position on
  			 * the right it corresponds, even though it doesn't add
  			 * any lines on the right. By moving above a plus chunk,
  			 * that position on the right has shifted. */
  			last = &result->head[result->len - 1];
  			new_chunk->right_start = last->right_start;
  
  			debug("  - added minus-chunk follows plus-chunk,"
  			      " put before that plus-chunk\n");
  		}
  
  		/* That last_t == CHUNK_PLUS indicates to which position on the
  		 * left it corresponds, even though it doesn't add any lines on
  		 * the left. By inserting/extending the prev_last_t ==
  		 * CHUNK_MINUS, that position on the left has shifted. */
  		last = &result->head[result->len - 1];
  		last->left_start = new_chunk->left_start
  			+ new_chunk->left_count;
  
  	} else {
  		ARRAYLIST_ADD(new_chunk, *result);
  		if (!new_chunk)
  			return NULL;
  		*new_chunk = *chunk;
  	}
  	return new_chunk;
  }
  
  /* Even if a left or right side is empty, diff output may need to know the
   * position in that file.
   * So left_start or right_start must never be NULL -- pass left_count or
   * right_count as zero to indicate staying at that position without consuming
   * any lines. */
  struct diff_chunk *
  diff_state_add_chunk(struct diff_state *state, bool solved,
  		     struct diff_atom *left_start, unsigned int left_count,
  		     struct diff_atom *right_start, unsigned int right_count)
  {
  	struct diff_chunk *new_chunk;
  	struct diff_chunk chunk = {
  		.solved = solved,
  		.left_start = left_start,
  		.left_count = left_count,
  		.right_start = right_start,
  		.right_count = right_count,
  	};
  
  	/* An unsolved chunk means store as intermediate result for later
  	 * re-iteration.
  	 * If there already are intermediate results, that means even a
  	 * following solved chunk needs to go to intermediate results, so that
  	 * it is later put in the final correct position in solved chunks.
  	 */
  	if (!solved || state->temp_result.len) {
  		/* Append to temp_result */
  		debug("ADD %s chunk to temp result:\n",
  		      chunk.solved ? "solved" : "UNSOLVED");
  		debug("L\n");
  		debug_dump_atoms(&state->left, left_start, left_count);
  		debug("R\n");
  		debug_dump_atoms(&state->right, right_start, right_count);
  		ARRAYLIST_ADD(new_chunk, state->temp_result);
  		if (!new_chunk)
  			return NULL;
  		*new_chunk = chunk;
  		return new_chunk;
  	}
  
  	return diff_state_add_solved_chunk(state, &chunk);
  }
  
  static void
  diff_data_init_root(struct diff_data *d, FILE *f, const uint8_t *data,
      unsigned long long len, int diff_flags)
  {
  	*d = (struct diff_data){
  		.f = f,
  		.pos = 0,
  		.data = data,
  		.len = len,
  		.root = d,
  		.diff_flags = diff_flags,
  	};
  }
  
  void
  diff_data_init_subsection(struct diff_data *d, struct diff_data *parent,
  			  struct diff_atom *from_atom, unsigned int atoms_count)
  {
  	struct diff_atom *last_atom;
  
  	debug("diff_data %p  parent %p  from_atom %p  atoms_count %u\n",
  	      d, parent, from_atom, atoms_count);
  	debug("  from_atom ");
  	debug_dump_atom(parent, NULL, from_atom);
  
  	if (atoms_count == 0) {
  		*d = (struct diff_data){
  			.f = NULL,
  			.pos = 0,
  			.data = NULL,
  			.len = 0,
  			.root = parent->root,
  			.atoms.head = NULL,
  			.atoms.len = atoms_count,
  		};
  
  		return;
  	}
  
  	last_atom = from_atom + atoms_count - 1;
  	*d = (struct diff_data){
  		.f = NULL,
  		.pos = from_atom->pos,
  		.data = from_atom->at,
  		.len = (last_atom->pos + last_atom->len) - from_atom->pos,
  		.root = parent->root,
  		.atoms.head = from_atom,
  		.atoms.len = atoms_count,
  	};
  
  	debug("subsection:\n");
  	debug_dump(d);
  }
  
  void
  diff_data_free(struct diff_data *diff_data)
  {
  	if (!diff_data)
  		return;
  	if (diff_data->atoms.allocated)
  		ARRAYLIST_FREE(diff_data->atoms);
  }
  
  int
  diff_algo_none(const struct diff_algo_config *algo_config,
  	       struct diff_state *state)
  {
  	debug("\n** %s\n", __func__);
  	debug("left:\n");
  	debug_dump(&state->left);
  	debug("right:\n");
  	debug_dump(&state->right);
  	debug_dump_myers_graph(&state->left, &state->right, NULL, NULL, 0, NULL,
  			       0);
  
  	/* Add a chunk of equal lines, if any */
  	struct diff_atom *l = state->left.atoms.head;
  	unsigned int l_len = state->left.atoms.len;
  	struct diff_atom *r = state->right.atoms.head;
  	unsigned int r_len = state->right.atoms.len;
  	unsigned int equal_atoms_start = 0;
  	unsigned int equal_atoms_end = 0;
  	unsigned int l_idx = 0;
  	unsigned int r_idx = 0;
  
  	while (equal_atoms_start < l_len
  	       && equal_atoms_start < r_len) {
  		int err;
  		bool same;
  		err = diff_atom_same(&same, &l[equal_atoms_start],
  				     &r[equal_atoms_start]);
  		if (err)
  			return err;
  		if (!same)
  			break;
  		equal_atoms_start++;
  	}
  	while (equal_atoms_end < (l_len - equal_atoms_start)
  	       && equal_atoms_end < (r_len - equal_atoms_start)) {
  		int err;
  		bool same;
  		err = diff_atom_same(&same, &l[l_len - 1 - equal_atoms_end],
  				   &r[r_len - 1 - equal_atoms_end]);
  		if (err)
  			return err;
  		if (!same)
  			break;
  		equal_atoms_end++;
  	}
  
  	/* Add a chunk of equal lines at the start */
  	if (equal_atoms_start) {
  		if (!diff_state_add_chunk(state, true,
  					  l, equal_atoms_start,
  					  r, equal_atoms_start))
  			return ENOMEM;
  		l_idx += equal_atoms_start;
  		r_idx += equal_atoms_start;
  	}
  
  	/* Add a "minus" chunk with all lines from the left. */
  	if (equal_atoms_start + equal_atoms_end < l_len) {
  		unsigned int add_len = l_len - equal_atoms_start - equal_atoms_end;
  		if (!diff_state_add_chunk(state, true,
  					  &l[l_idx], add_len,
  					  &r[r_idx], 0))
  			return ENOMEM;
  		l_idx += add_len;
  	}
  
  	/* Add a "plus" chunk with all lines from the right. */
  	if (equal_atoms_start + equal_atoms_end < r_len) {
  		unsigned int add_len = r_len - equal_atoms_start - equal_atoms_end;
  		if (!diff_state_add_chunk(state, true,
  					  &l[l_idx], 0,
  					  &r[r_idx], add_len))
  			return ENOMEM;
  		r_idx += add_len;
  	}
  
  	/* Add a chunk of equal lines at the end */
  	if (equal_atoms_end) {
  		if (!diff_state_add_chunk(state, true,
  					  &l[l_idx], equal_atoms_end,
  					  &r[r_idx], equal_atoms_end))
  			return ENOMEM;
  	}
  
  	return DIFF_RC_OK;
  }
  
  static int
  diff_run_algo(const struct diff_algo_config *algo_config,
  	      struct diff_state *state)
  {
  	int rc;
  
  	if (!algo_config || !algo_config->impl
  	    || !state->recursion_depth_left
  	    || !state->left.atoms.len || !state->right.atoms.len) {
  		debug("Fall back to diff_algo_none():%s%s%s\n",
  		      (!algo_config || !algo_config->impl) ? " no-cfg" : "",
  		      (!state->recursion_depth_left) ? " max-depth" : "",
  		      (!state->left.atoms.len || !state->right.atoms.len)?
  			      " trivial" : "");
  		return diff_algo_none(algo_config, state);
  	}
  
  	ARRAYLIST_FREE(state->temp_result);
  	ARRAYLIST_INIT(state->temp_result, DIFF_RESULT_ALLOC_BLOCKSIZE);
  	rc = algo_config->impl(algo_config, state);
  	switch (rc) {
  	case DIFF_RC_USE_DIFF_ALGO_FALLBACK:
  		debug("Got DIFF_RC_USE_DIFF_ALGO_FALLBACK (%p)\n",
  		      algo_config->fallback_algo);
  		rc = diff_run_algo(algo_config->fallback_algo, state);
  		goto return_rc;
  
  	case DIFF_RC_OK:
  		/* continue below */
  		break;
  
  	default:
  		/* some error happened */
  		goto return_rc;
  	}
  
  	/* Pick up any diff chunks that are still unsolved and feed to
  	 * inner_algo.  inner_algo will solve unsolved chunks and append to
  	 * result, and subsequent solved chunks on this level are then appended
  	 * to result afterwards. */
  	int i;
  	for (i = 0; i < state->temp_result.len; i++) {
  		struct diff_chunk *c = &state->temp_result.head[i];
  		if (c->solved) {
  			diff_state_add_solved_chunk(state, c);
  			continue;
  		}
  
  		/* c is an unsolved chunk, feed to inner_algo */
  		struct diff_state inner_state = {
  			.result = state->result,
  			.recursion_depth_left = state->recursion_depth_left - 1,
  			.kd_buf = state->kd_buf,
  			.kd_buf_size = state->kd_buf_size,
  		};
  		diff_data_init_subsection(&inner_state.left, &state->left,
  					  c->left_start, c->left_count);
  		diff_data_init_subsection(&inner_state.right, &state->right,
  					  c->right_start, c->right_count);
  
  		rc = diff_run_algo(algo_config->inner_algo, &inner_state);
  		state->kd_buf = inner_state.kd_buf;
  		state->kd_buf_size = inner_state.kd_buf_size;
  		if (rc != DIFF_RC_OK)
  			goto return_rc;
  	}
  
  	rc = DIFF_RC_OK;
  return_rc:
  	ARRAYLIST_FREE(state->temp_result);
  	return rc;
  }
  
  int
  diff_atomize_file(struct diff_data *d,
  		  const struct diff_config *config,
  		  FILE *f, const uint8_t *data, off_t len, int diff_flags)
  {
  	if (!config->atomize_func)
  		return EINVAL;
  
  	diff_data_init_root(d, f, data, len, diff_flags);
  
  	return config->atomize_func(config->atomize_func_data, d);
  
  }
  
  struct diff_result *
  diff_main(const struct diff_config *config, struct diff_data *left,
  	  struct diff_data *right)
  {
  	struct diff_result *result = malloc(sizeof(struct diff_result));
  	if (!result)
  		return NULL;
  
  	*result = (struct diff_result){};
  	result->left = left;
  	result->right = right;
  
  	struct diff_state state = {
  		.result = result,
  		.recursion_depth_left = config->max_recursion_depth ? : UINT_MAX,
  		.kd_buf = NULL,
  		.kd_buf_size = 0,
  	};
  	diff_data_init_subsection(&state.left, left,
  				  left->atoms.head,
  				  left->atoms.len);
  	diff_data_init_subsection(&state.right, right,
  				  right->atoms.head,
  				  right->atoms.len);
  
  	result->rc = diff_run_algo(config->algo, &state);
  	free(state.kd_buf);
  
  	return result;
  }
  
  void
  diff_result_free(struct diff_result *result)
  {
  	if (!result)
  		return;
  	ARRAYLIST_FREE(result->chunks);
  	free(result);
  }
  

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