first commit

.gitignore

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+# testing files
+build
+build.ninja
+ngen.toml
+tree.c
+tree.pdf
+tv.c

LICENSE.txt

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+                   GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+
+  This version of the GNU Lesser General Public License incorporates
+the terms and conditions of version 3 of the GNU General Public
+License, supplemented by the additional permissions listed below.
+
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README.md

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+# treeviz
+A header-only C library which uses [graphviz](https://www.graphviz.org/) to
+visualize recursive data structures.
+
+This library is intended mostly for debugging purposes, as it can oftentimes
+be useful to visualize your program's data layout. This is especially true with
+deeply nested recursive data structures.
+
+The methods in this library use two functions that end-user must write
+themselves:
+
+1. One that iterates over a node's children,
+1. And another that represents a node's data.
+
+This design allows the library to work with **any recursive data structure.**
+As it turns out, these two functions are all you need to generalize the task
+of visualization.
+
+## Dependencies
+You must have graphviz installed, and the `dot` executable in your path. That's
+it.
+
+*Optional:* Becuase this library renders your tree to a pdf (for now), it is
+nice to have a pdf viewer that updates the screen automatically upon an update
+to the file being viewed. [Zathura](https://github.com/pwmt/zathura) is one such
+viewer, but there are many available.
+
+## TODO: write documentation
+There are some notes in the header file that may guide you before I write the
+actual docs.
+
+---
+Copyright (C) Noah Swerhun under the terms of the LGPLv3 (see LICENSE.txt).

treeviz.h

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+#ifndef TREEVIZ_H
+#define TREEVIZ_H
+
+// TreeViz context. Contains settings for the visualizer functions. This
+// is wrapped in a struct so you don't have to always pass the same options
+// to every funcion call. However, if you want to do that, you can use the
+// `TV_vizl` function.
+typedef struct TVCtx_T {
+  // Output filename. Should end in `.pdf`
+  char *filename;
+
+  // Function that takes a reference to a node, and returns a string
+  // representing the node's data. The representation should not include any
+  // information about children, just the data stored in the node that the
+  // function was called on.
+  char *(*represent_data)(void *node);
+
+  // A function that takes a node, and iteratively returns each child of the
+  // node on each successive call, setting `done` to 1 when all children have
+  // been processed. Be sure to use `cur_idx` to track the function's progress:
+  // this function will be called in a recursive context, so using static memory
+  // introduces some funny bugs.
+  void *(*next_child)(void *root_node, int *done, int *cur_idx);
+} TVCtx;
+
+// Visualize the tree rooted at `root_node`, using the settings found in `ctx`.
+void TV_vizv(void *root_node, TVCtx *ctx);
+
+// Visualize the tree rooted at `root_node`, using the settings specifed. See
+// the `TVCtx` struct.
+void TV_vizl(void *root_node, char *filename,
+             char *(*represent_data)(void *root_node),
+             void *(*next_child)(void *root_node, int *done, int *cur_idx));
+
+#endif
+
+#ifdef TREEVIZ_IMPLEMENTATION
+#ifndef TREEVIZ_IMPL_ALREADY
+#define TREEVIZ_IMPL_ALREADY
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define ERRCHECK(...)                                                          \
+  if (errno != 0) {                                                            \
+    fprintf(stderr, "error: %s (errno %d)\n", strerror(errno), errno);         \
+    fprintf(stderr, __VA_ARGS__);                                              \
+    fputc('\n', stderr);                                                       \
+    assert(errno == 0);                                                        \
+  }
+
+#define NOT_NULL(x) assert(x != NULL)
+
+void _TV_write_dot(void *root_node, int fd, TVCtx *ctx, size_t *id) {
+  void *(*next_child)(void *root_node, int *done, int *cur_idx) =
+      ctx->next_child;
+  char *(*represent_data)(void *node) = ctx->represent_data;
+
+  char *repr = represent_data(root_node);
+
+  size_t cur_id = *id;
+  ++(*id);
+
+  errno = 0;
+  if (root_node == NULL) {
+    dprintf(fd, "%zu [style=filled,fillcolor=gray,label=\"%s\"];", cur_id,
+            repr);
+  } else {
+    dprintf(fd, "%zu [label=\"%s\"];", cur_id, repr);
+  }
+  ERRCHECK("TreeViz: _TV_write_dot: could not write to pipe");
+
+  free(repr);
+
+  if (root_node == NULL) {
+    return;
+  }
+
+  int done = 0;
+  int iter = 0;
+  while (!done) {
+    void *child = next_child(root_node, &done, &iter);
+
+    errno = 0;
+    dprintf(fd, "%zu->%zu;", cur_id, *id);
+    ERRCHECK("TreeViz: _TV_write_dot: could not write to pipe");
+
+    _TV_write_dot(child, fd, ctx, id);
+  }
+}
+
+void TV_vizv(void *root_node, TVCtx *ctx) {
+  int pipe_stdin[2];
+
+  errno = 0;
+  pipe(pipe_stdin);
+  ERRCHECK("TreeViz: TV_vizv: could not create pipe to dot")
+
+  int child_stdin_write = pipe_stdin[1];
+  int child_stdin_read = pipe_stdin[0];
+
+  char o_argument[1024] = "-o";
+  strncat(o_argument, ctx->filename, 1021);
+
+  errno = 0;
+  pid_t pid = fork();
+  ERRCHECK("TreeViz: TV_vizv: could not fork process");
+
+  if (pid == 0) {
+    //// CHILD PROCESS
+    close(child_stdin_write);
+    ERRCHECK("TreeViz: TV_vizv: CHILD: could not close old pipe, write end");
+
+    dup2(child_stdin_read, STDIN_FILENO);
+    ERRCHECK("TreeViz: TV_vizv: CHILD: could not set stdin fileno");
+
+    close(child_stdin_read);
+    ERRCHECK("TreeViz: TV_vizv: CHILD: could not close old pipe, read end");
+
+    char *run = "dot";
+    execlp(run, run, "-Tpdf", o_argument);
+    ERRCHECK("TreeViz: TV_vizv: CHILD: could not exec `%s`.\n\nDo you have "
+             "graphviz installed and in your PATH?\n",
+             run);
+  } else {
+    //// PARENT PROCESS
+    close(child_stdin_read);
+    ERRCHECK("TreeViz: TV_vizv: could not close old pipe, read end");
+
+    dprintf(child_stdin_write, "digraph{node [shape=rect];");
+    ERRCHECK("TreeViz: TV_vizv: could not write to pipe");
+
+    size_t id = 0;
+    _TV_write_dot(root_node, child_stdin_write, ctx, &id);
+
+    errno = 0;
+    dprintf(child_stdin_write, "}");
+    ERRCHECK("TreeViz: TV_vizv: could not write to pipe");
+
+    close(child_stdin_write);
+    ERRCHECK("TreeViz: TV_vizv: could not close old pipe, write end");
+
+    int status;
+    wait(&status);
+    ERRCHECK("TreeViz: TV_vizv: could not wait on child process");
+    if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+      fprintf(stderr, "TreeViz: TV_vizv: dot process failed. "
+                      "terminating immediately.\n");
+      assert(status == 0);
+    }
+  }
+}
+
+void TV_vizl(void *root_node, char *filename,
+             char *(*represent_data)(void *root_node),
+             void *(*next_child)(void *root_node, int *done, int *cur_idx)) {
+  TVCtx ctx = {filename, represent_data, next_child};
+  TV_vizv(root_node, &ctx);
+}
+
+#endif
+#endif