Add statement filter sink and serd-filter tool

2 files changed, 327 insertions, 0 deletions

diff --git a/tools/meson.build b/tools/meson.build
index ce82b212..43902c74 100644
--- a/tools/meson.build
+++ b/tools/meson.build
@@ -8,6 +8,15 @@ if get_option('static') and cc.get_id() != 'msvc'
   tool_link_args += ['-static']
 endif
 
+serd_filter = executable(
+  'serd-filter',
+  files('console.c', 'serd-filter.c'),
+  c_args: tool_c_args,
+  dependencies: [serd_dep, zix_dep],
+  install: true,
+  link_args: tool_link_args,
+)
+
 serd_pipe = executable(
   'serd-pipe',
   files('console.c', 'serd-pipe.c'),
@@ -17,4 +26,5 @@ serd_pipe = executable(
   link_args: tool_link_args,
 )
 
+meson.override_find_program('serd-filter', serd_filter)
 meson.override_find_program('serd-pipe', serd_pipe)
diff --git a/tools/serd-filter.c b/tools/serd-filter.c
new file mode 100644
index 00000000..01834e5a
--- /dev/null
+++ b/tools/serd-filter.c
@@ -0,0 +1,317 @@
+// Copyright 2011-2021 David Robillard <d@drobilla.net>
+// SPDX-License-Identifier: ISC
+
+#include "console.h"
+
+#include "serd/attributes.h"
+#include "serd/env.h"
+#include "serd/event.h"
+#include "serd/filter.h"
+#include "serd/input_stream.h"
+#include "serd/log.h"
+#include "serd/memory.h"
+#include "serd/node.h"
+#include "serd/nodes.h"
+#include "serd/reader.h"
+#include "serd/sink.h"
+#include "serd/statement.h"
+#include "serd/status.h"
+#include "serd/string_view.h"
+#include "serd/syntax.h"
+#include "serd/world.h"
+#include "serd/writer.h"
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/* Application (after parsing command-line arguments) */
+
+// All options
+typedef struct {
+  SerdCommonOptions common;
+  const char*       pattern;
+  const char*       pattern_file;
+  char* const*      inputs;
+  intptr_t          n_inputs;
+  bool              invert;
+} Options;
+
+// A single statement pattern
+typedef struct {
+  SerdNode* s;
+  SerdNode* p;
+  SerdNode* o;
+  SerdNode* g;
+} FilterPattern;
+
+// Context for the pattern event callback
+typedef struct {
+  SerdAllocator* allocator;
+  FilterPattern  pattern;
+} PatternEventContext;
+
+// Handler for events read from a pattern
+static SerdStatus
+on_pattern_event(void* const handle, const SerdEvent* const event)
+{
+  PatternEventContext* const ctx       = (PatternEventContext*)handle;
+  SerdAllocator* const       allocator = ctx->allocator;
+
+  if (event->type == SERD_STATEMENT) {
+    FilterPattern* const pat = &ctx->pattern;
+    if (pat->s) {
+      return SERD_BAD_PATTERN;
+    }
+
+    const SerdStatement* const statement = event->statement.statement;
+    pat->s = serd_node_copy(allocator, serd_statement_subject(statement));
+    pat->p = serd_node_copy(allocator, serd_statement_predicate(statement));
+    pat->o = serd_node_copy(allocator, serd_statement_object(statement));
+    pat->g = serd_node_copy(allocator, serd_statement_graph(statement));
+  }
+
+  return SERD_SUCCESS;
+}
+
+// Parse a pattern from some input and return a new filter for it
+static SerdSink*
+parse_pattern(SerdWorld* const       world,
+              const SerdSink* const  sink,
+              SerdInputStream* const in,
+              const bool             inclusive)
+{
+  SerdAllocator* const allocator = serd_world_allocator(world);
+  SerdEnv* const       env       = serd_env_new(allocator, serd_empty_string());
+  PatternEventContext  ctx       = {allocator, {NULL, NULL, NULL, NULL}};
+
+  SerdSink*   in_sink = serd_sink_new(allocator, &ctx, on_pattern_event, NULL);
+  SerdReader* reader =
+    serd_reader_new(world, SERD_NQUADS, SERD_READ_VARIABLES, env, in_sink);
+
+  const SerdNode* pattern_name =
+    serd_nodes_get(serd_world_nodes(world), serd_a_string("pattern"));
+
+  SerdStatus st = serd_reader_start(reader, in, pattern_name, 1);
+  if (!st) {
+    st = serd_reader_read_document(reader);
+  }
+
+  serd_close_input(in);
+  serd_reader_free(reader);
+  serd_env_free(env);
+  serd_sink_free(in_sink);
+
+  if (st) {
+    serd_logf(world,
+              SERD_LOG_LEVEL_ERROR,
+              "failed to parse pattern (%s)",
+              serd_strerror(st));
+    return NULL;
+  }
+
+  SerdSink* filter = serd_filter_new(world,
+                                     sink,
+                                     ctx.pattern.s,
+                                     ctx.pattern.p,
+                                     ctx.pattern.o,
+                                     ctx.pattern.g,
+                                     inclusive);
+
+  serd_node_free(allocator, ctx.pattern.s);
+  serd_node_free(allocator, ctx.pattern.p);
+  serd_node_free(allocator, ctx.pattern.o);
+  serd_node_free(allocator, ctx.pattern.g);
+  return filter;
+}
+
+SERD_LOG_FUNC(2, 3)
+static SerdStatus
+log_error(SerdWorld* const world, const char* const fmt, ...)
+{
+  va_list args;
+  va_start(args, fmt);
+
+  const SerdLogField file = {"SERD_FILE", "serd-filter"};
+  const SerdStatus   st =
+    serd_vxlogf(world, SERD_LOG_LEVEL_ERROR, 1, &file, fmt, args);
+
+  va_end(args);
+  return st;
+}
+
+// Run the tool using the given options
+static SerdStatus
+run(Options opts)
+{
+  SerdTool app = {{NULL, NULL, NULL, NULL}, NULL, NULL, NULL};
+
+  // Set up the writing environment
+  SerdStatus st = SERD_SUCCESS;
+  if ((st = serd_tool_setup(&app, "serd-filter", opts.common))) {
+    serd_tool_cleanup(app);
+    return st;
+  }
+
+  const SerdSink* const target = serd_writer_sink(app.writer);
+
+  // Open the pattern input (either a string or filename)
+  SerdInputStream pattern  = {NULL, NULL, NULL, NULL};
+  const char*     position = opts.pattern;
+  if (opts.pattern) {
+    pattern = serd_open_input_string(&position);
+  } else if (opts.pattern_file) {
+    pattern = serd_open_input_file(opts.pattern_file);
+  }
+
+  if (!pattern.stream) {
+    log_error(app.world, "failed to open pattern");
+    return SERD_BAD_STREAM;
+  }
+
+  // Set up the output pipeline: filter -> writer
+  SerdSink* const filter =
+    parse_pattern(app.world, target, &pattern, !opts.invert);
+  if (!filter) {
+    log_error(app.world, "failed to set up filter");
+    return SERD_UNKNOWN_ERROR;
+  }
+
+  serd_close_input(&pattern);
+
+  // Read all the inputs, which drives the writer to emit the output
+  if (!(st = serd_read_inputs(app.world,
+                              opts.common,
+                              app.env,
+                              opts.n_inputs,
+                              opts.inputs,
+                              filter))) {
+    st = serd_writer_finish(app.writer);
+  }
+
+  if (st) {
+    log_error(app.world, "failed to read input (%s)", serd_strerror(st));
+  }
+
+  serd_sink_free(filter);
+
+  const SerdStatus cst = serd_tool_cleanup(app);
+  return st ? st : cst;
+}
+
+/* Command-line interface (before setting up serd) */
+
+static int
+print_usage(const char* const name, const bool error)
+{
+  static const char* const description =
+    "Search for statements matching PATTERN in each INPUT.\n"
+    "INPUT can be a local filename, or \"-\" to read from standard input.\n\n"
+    "  -B BASE_URI      Base URI or path for resolving relative references.\n"
+    "  -I SYNTAX        Input syntax turtle/ntriples/trig/nquads, or option\n"
+    "                   lax/variables/relative/global/generated.\n"
+    "  -O SYNTAX        Output syntax empty/turtle/ntriples/nquads, or option\n"
+    "                   ascii/expanded/verbatim/terse/lax.\n"
+    "  -V               Display version information and exit.\n"
+    "  -f PATTERN_FILE  Read pattern from PATTERN_FILE instead.\n"
+    "  -h               Display this help and exit.\n"
+    "  -k BYTES         Parser stack size.\n"
+    "  -o FILENAME      Write output to FILENAME instead of stdout.\n"
+    "  -v               Invert filter to select non-matching statements.\n";
+
+  FILE* const os = error ? stderr : stdout;
+  fprintf(os, "%s", error ? "\n" : "");
+  fprintf(os, "Usage: %s [OPTION]... PATTERN [INPUT]...\n", name);
+  fprintf(os, "       %s [OPTION]... -f PATTERN_FILE [INPUT]...\n", name);
+  fprintf(os, "\n%s", description);
+  return error ? EXIT_FAILURE : EXIT_SUCCESS;
+}
+
+// Parse the option pointed to by `iter`, and advance it to the next one
+static SerdStatus
+parse_option(OptionIter* const iter, Options* const opts)
+{
+#define ARG_ERRORF(fmt, ...) \
+  fprintf(stderr, "%s: " fmt, iter->argv[0], __VA_ARGS__)
+
+  SerdStatus st = serd_parse_common_option(iter, &opts->common);
+  if (st != SERD_FAILURE) {
+    return st;
+  }
+
+  const char opt = iter->argv[iter->a][iter->f];
+
+  switch (opt) {
+  case 'V':
+    return serd_print_version("serd-filter");
+
+  case 'f':
+    return serd_get_argument(iter, &opts->pattern_file);
+
+  case 'h':
+    print_usage(iter->argv[0], false);
+    return SERD_FAILURE;
+
+  case 'v':
+    opts->invert = true;
+    return serd_option_iter_advance(iter);
+
+  default:
+    break;
+  }
+
+  ARG_ERRORF("invalid option -- '%c'\n", opt);
+  return SERD_BAD_ARG;
+
+#undef ARG_ERRORF
+}
+
+int
+main(int argc, char** argv)
+{
+  char  default_input[]  = "-";
+  char* default_inputs[] = {default_input};
+
+  Options opts = {{"",
+                   NULL,
+                   4096U,
+                   1048576U,
+                   {SERD_SYNTAX_EMPTY, 0U, false},
+                   {SERD_NQUADS, 0U, false}},
+                  NULL,
+                  NULL,
+                  NULL,
+                  0U,
+                  false};
+
+  // Parse all command line options (which must precede inputs)
+  SerdStatus st   = SERD_SUCCESS;
+  OptionIter iter = {argv, argc, 1, 1};
+  while (!serd_option_iter_is_end(iter)) {
+    if ((st = parse_option(&iter, &opts))) {
+      return (st == SERD_FAILURE) ? 0 : print_usage(argv[0], true);
+    }
+  }
+
+  // If -f isn't used, then the first positional argument is the pattern
+  if (!opts.pattern_file) {
+    opts.pattern = argv[iter.a++];
+  }
+
+  // Every argument past that is an input
+  opts.inputs   = argv + iter.a;
+  opts.n_inputs = argc - iter.a;
+  if (opts.n_inputs == 0) {
+    opts.n_inputs = 1;
+    opts.inputs   = default_inputs;
+  }
+
+  // Don't add prefixes to blank node labels if there is only one input
+  if (opts.n_inputs == 1) {
+    opts.common.input.flags |= SERD_READ_GLOBAL;
+  }
+
+  return run(opts) > SERD_FAILURE;
+}