gxi C shim

src/gerbil/gxi.c

@@ -0,0 +1,231 @@
+// gxi C shim: this is the gxi interpreter shim, which invokes gsi loading Gerbil
+// gxi was originally a shell script, but we've had it with the shebang madness in the
+//  various unix variants, so I wrote this.
+// © vyzo
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+extern char **environ;
+
+// these may be patched by configure/install
+static char *default_gerbil_home = NULL;
+static char *default_gerbil_gsi  = "gsi";
+
+static const char *usage = "Usage: %s [-v|-h] | [-:<runtime-options>] [--lang <language>] [[-] [-e <expr>] [file]] ...\n";
+
+void exec_gxi(char *gsi, char *gerbil_home, char *gerbil_lang, char *runtime_opts, int argc, char **argv);
+char **gxi_envp(char *gerbil_home, char *gerbil_lang);
+char **gxi_argv(char *gerbil_home, char *runtime_opts, int argc, char **argv);
+char **gxi_argv_script(char *gerbil_home, char *runtime_opts, int argc, char **argv);
+char **gxi_argv_interactive(char *gerbil_home, char *runtime_opts);
+
+int main(int argc, char **argv) {
+  // determine GERBIL_HOME
+  char *gerbil_home = getenv("GERBIL_HOME");
+  if (!gerbil_home) {
+    gerbil_home = default_gerbil_home;
+  }
+  if (!gerbil_home) {
+    fprintf(stderr, "Cannot determine GERBIL_HOME\n");
+    return 1;
+  }
+
+  // determine GERBIL_GSI
+  char *gerbil_gsi = getenv("GERBIL_GSI");
+  if (!gerbil_gsi) {
+    gerbil_gsi = default_gerbil_gsi;
+  }
+
+  int argp = 1;
+  char *gerbil_lang = NULL;
+  char *runtime_opts = NULL;
+  if (argc > 1) {
+    if (!strcmp(argv[1], "-h")) {
+      fprintf(stdout, usage, argv[0]);
+      return 0;
+    }
+
+    if (!strcmp(argv[1], "-v")) {
+      char *args[] = {"-e", "(displayln gerbil-greeting)"};
+      exec_gxi(gerbil_gsi, gerbil_home, NULL, NULL, 2, args);
+      return 2;
+    }
+
+    if (strlen(argv[1]) > 1 && argv[1][0] == '-' && argv[1][1] == ':') {
+      runtime_opts = argv[1];
+      argp++;
+    }
+
+    if ((argp < argc) && !strcmp(argv[argp], "--lang")) {
+      argp++;
+      if (argp < argc) {
+        gerbil_lang = argv[argp];
+        argp++;
+      } else {
+        fprintf(stderr, usage, argv[0]);
+        return 1;
+      }
+    }
+  }
+
+  exec_gxi(gerbil_gsi, gerbil_home, gerbil_lang, runtime_opts, argc - argp, argv + argp);
+  return 2;
+}
+
+void exec_gxi(char *gsi,
+              char *gerbil_home,
+              char *gerbil_lang,
+              char *runtime_opts,
+              int argc, char **argv) {
+  char **gsi_envp = gxi_envp(gerbil_home, gerbil_lang);
+  char **gsi_argv = gxi_argv(gerbil_home, runtime_opts, argc, argv);
+  // in glibc we have execvpe, but that's not specified by POSIX
+  // so we just munch the environ pointer to pass the new environment and be portable
+  environ = gsi_envp;
+  execvp(gsi, gsi_argv);
+  perror("execvpe");
+}
+
+char **gxi_envp(char *gerbil_home, char *gerbil_lang) {
+  // find environment length, excluding GERBIL_HOME and GERBIL_LANG
+  int envlen = 0;
+  for (char **p = environ; *p; p++) {
+    if (!strstr(*p, "GERBIL_HOME") && !strstr(*p, "GERBIL_LANG")) {
+      envlen++;
+    }
+  }
+
+  // create the environment pointer
+  // account for GERBIL_HOME and GERBIL_LANG (if specified) in the new environment
+  if (gerbil_lang) {
+    envlen += 2;
+  } else {
+    envlen++;
+  }
+  char **envp = malloc((envlen + 1) * sizeof(char*));
+  if (!envp) {
+    perror("malloc");
+    exit(3);
+  }
+  envp[envlen] = NULL;
+
+  int envix = 0;
+
+  // set GERBIL_HOME
+  char *gerbil_home_envp = malloc(strlen("GERBIL_HOME=") + strlen(gerbil_home) + 1);
+  if (!gerbil_home_envp) {
+    perror("malloc");
+    exit(3);
+  }
+  sprintf(gerbil_home_envp, "GERBIL_HOME=%s", gerbil_home);
+  envp[envix++] = gerbil_home_envp;
+
+  // set GERBIL_LANG
+  if (gerbil_lang) {
+    char *gerbil_lang_envp = malloc(strlen("GERBIL_LANG=") + strlen(gerbil_home) + 1);
+    if (!gerbil_home_envp) {
+      perror("malloc");
+      exit(3);
+    }
+    sprintf(gerbil_lang_envp, "GERBIL_LANG=%s", gerbil_lang);
+    envp[envix++] = gerbil_lang_envp;
+  }
+
+  // copy the rest of the environment
+  for (char **p = environ; *p; p++) {
+    if (!strstr(*p, "GERBIL_HOME") && !strstr(*p, "GERBIL_LANG")) {
+      envp[envix++] = *p;
+    }
+  }
+
+  return envp;
+}
+
+char **gxi_argv(char *gerbil_home, char *runtime_opts, int argc, char **argv) {
+  if (argc > 0) {
+    return gxi_argv_script(gerbil_home, runtime_opts, argc, argv);
+  } else {
+    return gxi_argv_interactive(gerbil_home, runtime_opts);
+  }
+}
+
+char **gxi_argv_script(char* gerbil_home, char *runtime_opts, int argc, char **argv) {
+  int arglen = 2 + argc;
+  if (runtime_opts) {
+    arglen++;
+  }
+
+  int argix = 0;
+
+  char **gsi_argv = malloc((arglen + 1) * sizeof(char*));
+  if (!gsi_argv) {
+    perror("malloc");
+    exit(3);
+  }
+  gsi_argv[arglen] = NULL;
+
+  gsi_argv[argix++] = "gsi";
+
+  if (runtime_opts) {
+    gsi_argv[argix++] = runtime_opts;
+  }
+
+  char *gxi_init = malloc(strlen(gerbil_home) + strlen("/lib/gxi-init") + 1);
+  if (!gxi_init) {
+    perror("malloc");
+    exit(3);
+  }
+  sprintf(gxi_init, "%s/lib/gxi-init", gerbil_home);
+  gsi_argv[argix++] = gxi_init;
+
+  for (int i = 0; i < argc; i++) {
+    gsi_argv[argix++] = argv[i];
+  }
+
+  return gsi_argv;
+}
+
+char **gxi_argv_interactive(char *gerbil_home, char *runtime_opts) {
+  int arglen = 4;
+  if (runtime_opts) {
+    arglen++;
+  }
+
+  int argix = 0;
+
+  char **gsi_argv = malloc((arglen + 1) * sizeof(char*));
+  if (!gsi_argv) {
+    perror("malloc");
+    exit(3);
+  }
+  gsi_argv[arglen] = NULL;
+
+  gsi_argv[argix++] = "gsi";
+
+  if (runtime_opts) {
+    gsi_argv[argix++] = runtime_opts;
+  }
+
+  char *gxi_init = malloc(strlen(gerbil_home) + strlen("/lib/gxi-init") + 1);
+  if (!gxi_init) {
+    perror("malloc");
+    exit(3);
+  }
+  sprintf(gxi_init, "%s/lib/gxi-init", gerbil_home);
+  gsi_argv[argix++] = gxi_init;
+
+  char *gxi_interactive = malloc(strlen(gerbil_home) + strlen("/lib/gxi-interactive") + 1);
+  if (!gxi_interactive) {
+    perror("malloc");
+    exit(3);
+  }
+  sprintf(gxi_interactive, "%s/lib/gxi-interactive", gerbil_home);
+  gsi_argv[argix++] = gxi_interactive;
+
+  gsi_argv[argix++] = "-";
+
+  return gsi_argv;
+}