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ekp/ekp_c/ekp_kp.c
Kinneyzhang fd1210e557 fix: close repository audit findings 
Complete task002 through task016 across cache correctness, editor lifecycle, C boundaries, build and release governance, dictionary provenance, performance, interactive workflows, tests, documentation, and final cleanup.
2026-07-28 22:43:10 +08:00

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/*
* ekp_kp.c - Knuth-Plass line breaking algorithm
*
* Copyright (C) 2024-2026 Kinney Zhang
* SPDX-License-Identifier: GPL-3.0-or-later
*
* This file is part of emacs-kp, which is free software: you can
* redistribute it and/or modify it under the terms of the GNU General
* Public License as published by the Free Software Foundation, either
* version 3 of the License, or (at your option) any later version.
* It is distributed WITHOUT ANY WARRANTY; see the GNU General Public
* License (COPYING) for details.
*
* The heart of the system. O(n²) worst case, but with pruning and
* parallel candidate evaluation, typically O(n·m) where m is avg line length.
*
* Key optimizations:
* - Prefix sums for O(1) range queries
* - Early termination when line too long
* - Parallel demerits computation for large paragraphs
*/
#include "ekp_module.h"
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <float.h>
/* Global state */
ekp_state_t *ekp_global = NULL;
/* Fitness classes */
#define FITNESS_TIGHT 0
#define FITNESS_DECENT 1
#define FITNESS_LOOSE 2
#define FITNESS_VERY_LOOSE 3
/* Infinite badness: capped at 10000 like TeX (and the Elisp engine).
* NOT EKP_INFINITY: a badness-10000 line is terrible but still usable,
* matching ekp--compute-badness in ekp.el exactly. */
#define EKP_BADNESS_INF 10000.0
/* Badness computation */
static inline double compute_badness(int64_t adjustment, int64_t flexibility)
{
if (adjustment == 0)
return 0.0;
if (flexibility <= 0)
return EKP_BADNESS_INF;
double ratio = (double)adjustment / flexibility;
double badness = 100.0 * fabs(ratio * ratio * ratio);
return badness > EKP_BADNESS_INF ? EKP_BADNESS_INF : badness;
}
/* Fitness classification */
static inline uint8_t compute_fitness(int64_t adjustment, int64_t flexibility)
{
if (flexibility <= 0)
return FITNESS_DECENT;
double ratio = (double)adjustment / flexibility;
if (ratio < -0.5)
return FITNESS_TIGHT;
if (ratio < 0.5)
return FITNESS_DECENT;
if (ratio < 1.0)
return FITNESS_LOOSE;
return FITNESS_VERY_LOOSE;
}
/* Full demerits computation */
static inline double compute_demerits(double badness, int32_t penalty,
uint8_t prev_fitness, uint8_t curr_fitness,
bool end_hyphen, int prev_hyphen_count,
int line_penalty, int fitness_penalty,
int consec_hyphen_penalty)
{
/* Base: (line_penalty + badness)² */
double base = (line_penalty + badness);
base = base * base;
/* Add break penalty squared */
base += (double)penalty * penalty;
/* Fitness incompatibility */
int delta = abs((int)prev_fitness - (int)curr_fitness);
if (delta > 1)
base += fitness_penalty;
/* Consecutive hyphen penalty (quadratic growth) */
if (end_hyphen) {
int count = prev_hyphen_count + 1;
base += (double)consec_hyphen_penalty * count * count;
}
return base;
}
/*
* Unified DP input structure for the array-based DP core.
*/
typedef struct {
/* Prefix sum arrays */
const int32_t *ideal_prefix;
const int32_t *min_prefix;
const int32_t *max_prefix;
/* Glue arrays (nullable) */
const int32_t *glue_ideals;
const int32_t *glue_shrinks;
const int32_t *glue_stretches;
/* Hyphen info */
const int32_t *hyphen_positions;
size_t hyphen_count;
int32_t hyphen_width;
/* Forbidden break positions (kinsoku, no-break spans): sorted gap
* indices where a line may NOT end. Nullable. */
const int32_t *forbidden_positions;
size_t forbidden_count;
/* Right-edge protrusion (nullable, n+1): pixels the line's final
* glyph may hang past the flush edge when breaking at gap k;
* hyphen_protrude is the same for soft hyphens. */
const int32_t *tail_protrudes;
int32_t hyphen_protrude;
/* Space-box run widths (nullable, n+1 elements each):
* lead_spaces[i] = width of space-box run starting at box i
* trail_spaces[k] = width of space-box run ending at box k-1
* These runs are stripped by the renderer, so line metrics
* exclude them (matching ekp.el). */
const int32_t *lead_spaces;
const int32_t *trail_spaces;
/* Dimensions */
size_t n; /* box count */
int32_t line_width;
/* Width of line 0 (first-line indent support); equals line_width
* when no indent is active. In the forward DP a line starts at
* box 0 exactly when i == 0, so this needs no extra state. */
int32_t first_line_width;
/* K-P parameters */
int line_penalty;
int hyphen_penalty;
int fitness_penalty;
double last_line_ratio;
int consec_hyphen_penalty;
double last_line_short_penalty;
/* Per-line flexibility for non-justify alignment (0 = justify):
* widens max_w, so flexibility = max_w - ideal includes it. */
int32_t extra_stretch;
/* Two-pass strategy: strict K-P first; emergency single-box
* breaks only in the second pass (when no valid layout exists). */
bool allow_emergency;
} dp_input_t;
/*
* Shared hyphen position check for dp_input_t
*/
static inline bool dp_is_hyphen(const dp_input_t *in, size_t pos)
{
if (!in->hyphen_positions || in->hyphen_count == 0)
return false;
/* Binary search in sorted positions */
size_t lo = 0;
size_t hi = in->hyphen_count - 1;
while (lo < hi) {
size_t mid = lo + (hi - lo) / 2;
if ((size_t)in->hyphen_positions[mid] < pos)
lo = mid + 1;
else
hi = mid;
}
return (size_t)in->hyphen_positions[lo] == pos;
}
/*
* Shared forbidden-break check for dp_input_t (binary search).
*/
static inline bool dp_is_forbidden(const dp_input_t *in, size_t pos)
{
if (!in->forbidden_positions || in->forbidden_count == 0)
return false;
size_t lo = 0;
size_t hi = in->forbidden_count - 1;
while (lo < hi) {
size_t mid = lo + (hi - lo) / 2;
if ((size_t)in->forbidden_positions[mid] < pos)
lo = mid + 1;
else
hi = mid;
}
return (size_t)in->forbidden_positions[lo] == pos;
}
/*
* Core DP algorithm - shared by both entry points
* Processes position i, trying all end positions k.
* Updates output arrays when better solutions found.
*/
/*
* Emergency break: record a single-box over/underfull line so that the
* DP can never dead-end (every reachable i can always record i+1).
* Demerits are at least as bad as the worst regular line, so these are
* only chosen when nothing better exists. Mirrors
* ekp--dp-relax-emergency in ekp.el.
*/
static inline void dp_relax_emergency(
const dp_input_t *in, size_t i, size_t k,
double prev_dem, int prev_hyph, int prev_lines,
int64_t rest, bool end_hyphen,
double *demerits, int32_t *backptrs, int64_t *rest_pixels,
uint8_t *fitness, int32_t *hyphen_counts, int32_t *line_counts)
{
double base = in->line_penalty + EKP_BADNESS_INF;
double dem = prev_dem + base * base + (double)rest * rest;
if (dem < demerits[k]) {
demerits[k] = dem;
backptrs[k] = i;
rest_pixels[k] = rest;
fitness[k] = FITNESS_VERY_LOOSE;
hyphen_counts[k] = end_hyphen ? prev_hyph + 1 : 0;
line_counts[k] = prev_lines + 1;
}
}
static void dp_process_position(
const dp_input_t *in,
size_t i,
/* Input state at position i */
double prev_dem,
uint8_t prev_fit,
int prev_hyph,
int prev_lines,
/* Output arrays */
double *demerits,
int32_t *backptrs,
int64_t *rest_pixels,
uint8_t *fitness,
int32_t *hyphen_counts,
int32_t *line_counts)
{
size_t n = in->n;
/* Line 0 (i == 0) may have a different width: first-line indent */
int64_t line_width = (i == 0 && in->first_line_width > 0)
? in->first_line_width
: in->line_width;
/* Get leading glue for line starting at i */
int64_t lead_ideal = (in->glue_ideals && i < n) ? in->glue_ideals[i] : 0;
int64_t lead_shrink = (in->glue_shrinks && i < n) ? in->glue_shrinks[i] : 0;
int64_t lead_stretch = (in->glue_stretches && i < n) ? in->glue_stretches[i] : 0;
int64_t lead_space = in->lead_spaces ? in->lead_spaces[i] : 0;
/* Try extending to each position k > i */
bool saw_allowed = false;
for (size_t k = i + 1; k <= n; k++) {
bool is_last = (k == n);
/* Break forbidden here (kinsoku, no-break span): not a
* candidate; keep extending the line. */
if (!is_last && dp_is_forbidden(in, k))
continue;
bool is_single_box = (k == i + 1);
/* No permitted break strictly inside [i, k): the run is atomic
* and eligible for emergency handling, like a single box. */
bool atomic_run = !saw_allowed;
saw_allowed = true;
bool end_hyphen = dp_is_hyphen(in, k - 1);
int64_t hyph_w = end_hyphen ? in->hyphen_width : 0;
/* Right-edge protrusion widens this candidate's target */
int64_t lw = line_width +
(end_hyphen ? in->hyphen_protrude
: (in->tail_protrudes ? in->tail_protrudes[k] : 0));
/* Line metrics from i to k, excluding leading glue and the
* space-box runs the renderer strips (leading + trailing). */
int64_t raw_ideal = (int64_t)in->ideal_prefix[k] -
in->ideal_prefix[i] - lead_ideal;
int64_t space_w = lead_space +
(in->trail_spaces ? in->trail_spaces[k] : 0);
if (space_w > raw_ideal)
space_w = raw_ideal;
int64_t ideal = raw_ideal - space_w + hyph_w;
int64_t min_w = (int64_t)in->min_prefix[k] - in->min_prefix[i] -
(lead_ideal - lead_shrink) - space_w + hyph_w;
int64_t max_w = (int64_t)in->max_prefix[k] - in->max_prefix[i] -
(lead_ideal + lead_stretch) - space_w + hyph_w +
in->extra_stretch;
/* Too long? (last line is never shrunk below its ideal) */
if (min_w > lw || (is_last && ideal > lw)) {
if (atomic_run && in->allow_emergency)
dp_relax_emergency(in, i, k, prev_dem, prev_hyph, prev_lines,
lw - ideal, end_hyphen,
demerits, backptrs, rest_pixels,
fitness, hyphen_counts, line_counts);
break; /* No point trying longer lines */
}
/* Valid break? */
bool valid = (min_w <= lw && max_w >= lw) ||
(is_last && ideal <= lw);
if (!valid) {
/* Rigid underfull atomic run: emergency-record so the
* position after it stays reachable (2nd pass only). */
if (atomic_run && in->allow_emergency)
dp_relax_emergency(in, i, k, prev_dem, prev_hyph, prev_lines,
lw - ideal, end_hyphen,
demerits, backptrs, rest_pixels,
fitness, hyphen_counts, line_counts);
continue;
}
/* Compute demerits */
int64_t adjustment = lw - ideal;
int64_t flexibility = (adjustment > 0) ?
(max_w - ideal) : (ideal - min_w);
double badness;
uint8_t fit;
double dem;
/* Single-box line: use fixed flexibility=1, fitness=decent.
* This must come BEFORE is_last check to match Elisp behavior. */
if (is_single_box) {
badness = compute_badness(adjustment, 1);
fit = FITNESS_DECENT;
int penalty = end_hyphen ? in->hyphen_penalty : 0;
dem = prev_dem + compute_demerits(badness, penalty,
prev_fit, fit,
end_hyphen, prev_hyph,
in->line_penalty,
in->fitness_penalty,
in->consec_hyphen_penalty);
} else if (is_last) {
/* Last line: minimal penalty if reasonably filled */
double fill_ratio = (double)ideal / lw;
if (fill_ratio < in->last_line_ratio) {
badness = in->last_line_short_penalty * (1.0 - fill_ratio);
} else {
badness = 0.0;
}
fit = FITNESS_DECENT;
dem = prev_dem + (in->line_penalty + badness) *
(in->line_penalty + badness);
} else {
badness = compute_badness(adjustment, flexibility);
fit = compute_fitness(adjustment, flexibility);
int penalty = end_hyphen ? in->hyphen_penalty : 0;
dem = prev_dem + compute_demerits(badness, penalty,
prev_fit, fit,
end_hyphen, prev_hyph,
in->line_penalty,
in->fitness_penalty,
in->consec_hyphen_penalty);
}
/* Update if better */
if (dem < demerits[k]) {
demerits[k] = dem;
backptrs[k] = i;
rest_pixels[k] = adjustment;
fitness[k] = fit;
hyphen_counts[k] = end_hyphen ? prev_hyph + 1 : 0;
line_counts[k] = prev_lines + 1;
}
}
}
void ekp_result_destroy(ekp_result_t *r)
{
if (!r)
return;
free(r->breaks);
free(r->rest_pixels);
free(r);
}
/*
* Pure DP with pre-computed prefix arrays (for Elisp integration)
*
* This is the preferred API when Elisp has already computed everything.
* Elisp does: tokenization, width measurement, glue computation, prefix sums.
* C module only does: O(n²) DP computation.
*
* All font-dependent calculations happen in Elisp. C module is pure algorithm.
*
* Note: This function now uses dp_process_position() for the core DP logic,
* sharing the same algorithm with process_dp_range(). Any bug fix only needs
* to be made once in dp_process_position().
*/
ekp_result_t *ekp_break_with_prefixes(
const int32_t *ideal_prefix,
const int32_t *min_prefix,
const int32_t *max_prefix,
const int32_t *glue_ideals,
const int32_t *glue_shrinks,
const int32_t *glue_stretches,
size_t n,
const int32_t *hyphen_positions,
size_t hyphen_count,
int32_t hyphen_width,
int32_t line_width,
const int32_t *lead_spaces,
const int32_t *trail_spaces,
const int32_t *forbidden_positions,
size_t forbidden_count,
const int32_t *tail_protrudes,
int32_t hyphen_protrude,
int32_t first_line_width)
{
if (!ideal_prefix || !min_prefix || !max_prefix || n == 0 ||
n > INT32_MAX || line_width <= 0)
return NULL;
if (first_line_width <= 0)
first_line_width = line_width;
/* Allocate DP arrays */
double *demerits = malloc((n + 1) * sizeof(double));
int32_t *backptrs = malloc((n + 1) * sizeof(int32_t));
int64_t *rest_pixels = malloc((n + 1) * sizeof(int64_t));
uint8_t *fitness = malloc((n + 1) * sizeof(uint8_t));
int32_t *hyph_counts = malloc((n + 1) * sizeof(int32_t));
int32_t *line_counts = malloc((n + 1) * sizeof(int32_t));
if (!demerits || !backptrs || !rest_pixels || !fitness || !hyph_counts || !line_counts) {
free(demerits); free(backptrs); free(rest_pixels);
free(fitness); free(hyph_counts); free(line_counts);
return NULL;
}
/* Initialize */
for (size_t i = 0; i <= n; i++) {
demerits[i] = EKP_INFINITY;
backptrs[i] = -1;
rest_pixels[i] = 0;
fitness[i] = FITNESS_DECENT;
hyph_counts[i] = 0;
line_counts[i] = 0;
}
demerits[0] = 0.0;
/* Get K-P parameters */
int lp = ekp_global ? ekp_global->line_penalty : 10;
int hp = ekp_global ? ekp_global->hyphen_penalty : 50;
int fp = ekp_global ? ekp_global->fitness_penalty : 100;
double last_ratio = ekp_global ? ekp_global->last_line_ratio : 0.5;
int chp = ekp_global ? ekp_global->consec_hyphen_penalty : 100;
double llsp = ekp_global ? ekp_global->last_line_short_penalty : 50.0;
int32_t xstretch = ekp_global ? ekp_global->extra_stretch : 0;
/* Create unified input structure */
dp_input_t in = {
.ideal_prefix = ideal_prefix,
.min_prefix = min_prefix,
.max_prefix = max_prefix,
.glue_ideals = glue_ideals,
.glue_shrinks = glue_shrinks,
.glue_stretches = glue_stretches,
.hyphen_positions = hyphen_positions,
.hyphen_count = hyphen_count,
.hyphen_width = hyphen_width,
.forbidden_positions = forbidden_positions,
.forbidden_count = forbidden_count,
.tail_protrudes = tail_protrudes,
.hyphen_protrude = hyphen_protrude,
.lead_spaces = lead_spaces,
.trail_spaces = trail_spaces,
.n = n,
.line_width = line_width,
.first_line_width = first_line_width,
.line_penalty = lp,
.hyphen_penalty = hp,
.fitness_penalty = fp,
.last_line_ratio = last_ratio,
.consec_hyphen_penalty = chp,
.last_line_short_penalty = llsp,
.extra_stretch = xstretch,
.allow_emergency = false
};
/* Two passes: strict Knuth-Plass first; if the paragraph end is
* unreachable, rerun permitting emergency single-box breaks.
* Mirrors ekp--dp-cache-elisp. */
for (int pass = 0; pass < 2; pass++) {
in.allow_emergency = (pass == 1);
for (size_t i = 0; i <= n; i++) {
demerits[i] = EKP_INFINITY;
backptrs[i] = -1;
rest_pixels[i] = 0;
fitness[i] = FITNESS_DECENT;
hyph_counts[i] = 0;
line_counts[i] = 0;
}
demerits[0] = 0.0;
/* DP: for each valid start, try all ends */
for (size_t i = 0; i < n; i++) {
if (demerits[i] >= EKP_INFINITY)
continue;
dp_process_position(&in, i,
demerits[i],
fitness[i],
hyph_counts[i],
line_counts[i],
demerits,
backptrs,
rest_pixels,
fitness,
hyph_counts,
line_counts);
}
if (demerits[n] < EKP_INFINITY)
break;
}
/* Unreachable even with emergency breaks: cannot happen, but be safe */
if (demerits[n] >= EKP_INFINITY) {
free(demerits); free(backptrs); free(rest_pixels);
free(fitness); free(hyph_counts); free(line_counts);
return NULL;
}
/* Build result */
ekp_result_t *result = calloc(1, sizeof(*result));
if (!result) {
free(demerits); free(backptrs); free(rest_pixels);
free(fitness); free(hyph_counts); free(line_counts);
return NULL;
}
/* Count breaks */
size_t break_count = 0;
int32_t idx = n;
while (idx > 0) {
break_count++;
idx = backptrs[idx];
if (idx < 0) break;
}
result->breaks = malloc(break_count * sizeof(int32_t));
result->rest_pixels = malloc(break_count * sizeof(int64_t));
if (!result->breaks || !result->rest_pixels) {
ekp_result_destroy(result);
free(demerits); free(backptrs); free(rest_pixels);
free(fitness); free(hyph_counts); free(line_counts);
return NULL;
}
result->break_count = break_count;
result->total_cost = demerits[n];
/* Fill in reverse order */
idx = n;
for (size_t i = break_count; i > 0; i--) {
result->breaks[i - 1] = idx;
result->rest_pixels[i - 1] = rest_pixels[idx];
idx = backptrs[idx];
}
free(demerits); free(backptrs); free(rest_pixels);
free(fitness); free(hyph_counts); free(line_counts);
return result;
}
/*
* Work item for batch processing
*/
typedef struct {
ekp_batch_input_t *input;
ekp_result_t *result;
} batch_work_t;
static void batch_worker(void *arg)
{
batch_work_t *work = (batch_work_t *)arg;
ekp_batch_input_t *in = work->input;
work->result = ekp_break_with_prefixes(
in->ideal_prefix, in->min_prefix, in->max_prefix,
in->glue_ideals, in->glue_shrinks, in->glue_stretches,
in->n,
in->hyphen_positions, in->hyphen_count,
in->hyphen_width, in->line_width,
in->lead_spaces, in->trail_spaces,
in->forbidden_positions, in->forbidden_count,
in->tail_protrudes, in->hyphen_protrude,
in->first_line_width);
}
/*
* Batch line breaking: process multiple paragraphs in parallel
*
* This is the correct parallelization - each paragraph is completely
* independent, so we get linear speedup with zero synchronization overhead.
*/
ekp_result_t **ekp_break_batch(ekp_batch_input_t *inputs, size_t count)
{
if (!inputs || count == 0)
return NULL;
ekp_result_t **results = calloc(count, sizeof(ekp_result_t *));
if (!results)
return NULL;
/* Create the worker pool on first parallel use */
if (count > 1 && ekp_global && !ekp_global->pool)
ekp_global->pool = ekp_pool_create(0);
/* Single paragraph: no point using threads */
if (count == 1 || !ekp_global || !ekp_global->pool) {
for (size_t i = 0; i < count; i++) {
ekp_batch_input_t *in = &inputs[i];
results[i] = ekp_break_with_prefixes(
in->ideal_prefix, in->min_prefix, in->max_prefix,
in->glue_ideals, in->glue_shrinks, in->glue_stretches,
in->n,
in->hyphen_positions, in->hyphen_count,
in->hyphen_width, in->line_width,
in->lead_spaces, in->trail_spaces,
in->forbidden_positions, in->forbidden_count,
in->tail_protrudes, in->hyphen_protrude,
in->first_line_width);
}
return results;
}
/* Multiple paragraphs: parallel processing */
batch_work_t *works = malloc(count * sizeof(batch_work_t));
if (!works) {
/* Fallback to sequential */
for (size_t i = 0; i < count; i++) {
ekp_batch_input_t *in = &inputs[i];
results[i] = ekp_break_with_prefixes(
in->ideal_prefix, in->min_prefix, in->max_prefix,
in->glue_ideals, in->glue_shrinks, in->glue_stretches,
in->n,
in->hyphen_positions, in->hyphen_count,
in->hyphen_width, in->line_width,
in->lead_spaces, in->trail_spaces,
in->forbidden_positions, in->forbidden_count,
in->tail_protrudes, in->hyphen_protrude,
in->first_line_width);
}
return results;
}
/* Submit all work items */
for (size_t i = 0; i < count; i++) {
works[i].input = &inputs[i];
works[i].result = NULL;
ekp_pool_submit(ekp_global->pool, batch_worker, &works[i]);
}
/* Wait for all to complete */
ekp_pool_wait(ekp_global->pool);
/* Collect results */
for (size_t i = 0; i < count; i++) {
results[i] = works[i].result;
}
free(works);
return results;
}
/*
* Initialization and cleanup
*/
int ekp_init(void)
{
if (ekp_global)
return 0;
ekp_global = calloc(1, sizeof(*ekp_global));
if (!ekp_global)
return -1;
/* Default K-P parameters */
ekp_global->line_penalty = 10;
ekp_global->hyphen_penalty = 50;
ekp_global->fitness_penalty = 100;
ekp_global->last_line_ratio = 0.5;
ekp_global->consec_hyphen_penalty = 100;
ekp_global->last_line_short_penalty = 50.0;
/* The thread pool is created lazily by the first batch call:
* plain single-paragraph use never starts worker threads. */
ekp_global->pool = NULL;
return 0;
}
void ekp_cleanup(void)
{
if (!ekp_global)
return;
ekp_pool_destroy(ekp_global->pool);
free(ekp_global);
ekp_global = NULL;
}
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