filter: basic write hooking infrastructure

[ps-cgit] / filter.c

diff --git a/filter.c b/filter.c
index 80cf68956bc5291a74cbe029ebf449af625bedb0..f5a5992748d76af5733fe8c1135f09f6b4f5455c 100644 (file)
--- a/filter.c
+++ b/filter.c
@@ -12,16 +12,69 @@
 #include <unistd.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
 #include <stdlib.h>

+#include <dlfcn.h>

 
 

-int cgit_open_filter(struct cgit_filter *filter, ...)
+static ssize_t (*libc_write)(int fd, const void *buf, size_t count);
+static ssize_t (*filter_write)(struct cgit_filter *base, const void *buf, size_t count) = NULL;
+static struct cgit_filter *current_write_filter = NULL;
+
+static inline void reap_filter(struct cgit_filter *filter)
+{
+       if (filter && filter->cleanup)
+               filter->cleanup(filter);
+}
+
+void cgit_cleanup_filters(void)

 {
        int i;
 {
        int i;

-       va_list ap;
+       reap_filter(ctx.cfg.about_filter);
+       reap_filter(ctx.cfg.commit_filter);
+       reap_filter(ctx.cfg.source_filter);
+       for (i = 0; i < cgit_repolist.count; ++i) {
+               reap_filter(cgit_repolist.repos[i].about_filter);
+               reap_filter(cgit_repolist.repos[i].commit_filter);
+               reap_filter(cgit_repolist.repos[i].source_filter);
+       }
+}

 
 

-       va_start(ap, filter);
-       for (i = 0; i < filter->extra_args; i++)
+void cgit_init_filters(void)
+{
+       libc_write = dlsym(RTLD_NEXT, "write");
+       if (!libc_write)
+               die("Could not locate libc's write function");
+}
+
+ssize_t write(int fd, const void *buf, size_t count)
+{
+       if (fd != STDOUT_FILENO || !filter_write)
+               return libc_write(fd, buf, count);
+       return filter_write(current_write_filter, buf, count);
+}
+
+static inline void hook_write(struct cgit_filter *filter, ssize_t (*new_write)(struct cgit_filter *base, const void *buf, size_t count))
+{
+       /* We want to avoid buggy nested patterns. */
+       assert(filter_write == NULL);
+       assert(current_write_filter == NULL);
+       current_write_filter = filter;
+       filter_write = new_write;
+}
+
+static inline void unhook_write()
+{
+       assert(filter_write != NULL);
+       assert(current_write_filter != NULL);
+       filter_write = NULL;
+       current_write_filter = NULL;
+}
+
+static int open_exec_filter(struct cgit_filter *base, va_list ap)
+{
+       struct cgit_exec_filter *filter = (struct cgit_exec_filter *) base;
+       int i;
+
+       for (i = 0; i < filter->base.argument_count; i++)

                filter->argv[i+1] = va_arg(ap, char *);
                filter->argv[i+1] = va_arg(ap, char *);

-       va_end(ap);

 
        filter->old_stdout = chk_positive(dup(STDOUT_FILENO),
                "Unable to duplicate STDOUT");
 
        filter->old_stdout = chk_positive(dup(STDOUT_FILENO),
                "Unable to duplicate STDOUT");


@@ -41,9 +94,9 @@ int cgit_open_filter(struct cgit_filter *filter, ...)
        return 0;
 }
 
        return 0;
 }
 

-
-int cgit_close_filter(struct cgit_filter *filter)
+static int close_exec_filter(struct cgit_filter *base)

 {
 {

+       struct cgit_exec_filter *filter = (struct cgit_exec_filter *) base;

        int i, exit_status;
 
        chk_non_negative(dup2(filter->old_stdout, STDOUT_FILENO),
        int i, exit_status;
 
        chk_non_negative(dup2(filter->old_stdout, STDOUT_FILENO),


@@ -57,44 +110,129 @@ int cgit_close_filter(struct cgit_filter *filter)
        die("Subprocess %s exited abnormally", filter->cmd);
 
 done:
        die("Subprocess %s exited abnormally", filter->cmd);
 
 done:

-       for (i = 0; i < filter->extra_args; i++)
+       for (i = 0; i < filter->base.argument_count; i++)

                filter->argv[i+1] = NULL;
        return 0;
 
 }
 
                filter->argv[i+1] = NULL;
        return 0;
 
 }
 

+static void fprintf_exec_filter(struct cgit_filter *base, FILE *f, const char *prefix)
+{
+       struct cgit_exec_filter *filter = (struct cgit_exec_filter *) base;
+       fprintf(f, "%sexec:%s\n", prefix, filter->cmd);
+}
+
+static void cleanup_exec_filter(struct cgit_filter *base)
+{
+       struct cgit_exec_filter *filter = (struct cgit_exec_filter *) base;
+       if (filter->argv) {
+               free(filter->argv);
+               filter->argv = NULL;
+       }
+       if (filter->cmd) {
+               free(filter->cmd);
+               filter->cmd = NULL;
+       }
+}
+
+static struct cgit_filter *new_exec_filter(const char *cmd, int argument_count)
+{
+       struct cgit_exec_filter *f;
+       int args_size = 0;
+
+       f = xmalloc(sizeof(*f));
+       /* We leave argv for now and assign it below. */
+       cgit_exec_filter_init(f, xstrdup(cmd), NULL);
+       f->base.argument_count = argument_count;
+       args_size = (2 + argument_count) * sizeof(char *);
+       f->argv = xmalloc(args_size);
+       memset(f->argv, 0, args_size);
+       f->argv[0] = f->cmd;
+       return &f->base;
+}
+
+void cgit_exec_filter_init(struct cgit_exec_filter *filter, char *cmd, char **argv)
+{
+       memset(filter, 0, sizeof(*filter));
+       filter->base.open = open_exec_filter;
+       filter->base.close = close_exec_filter;
+       filter->base.fprintf = fprintf_exec_filter;
+       filter->base.cleanup = cleanup_exec_filter;
+       filter->cmd = cmd;
+       filter->argv = argv;
+       /* The argument count for open_filter is zero by default, unless called from new_filter, above. */
+       filter->base.argument_count = 0;
+}
+
+int cgit_open_filter(struct cgit_filter *filter, ...)
+{
+       int result;
+       va_list ap;
+       va_start(ap, filter);
+       result = filter->open(filter, ap);
+       va_end(ap);
+       return result;
+}
+
+int cgit_close_filter(struct cgit_filter *filter)
+{
+       return filter->close(filter);
+}
+

 void cgit_fprintf_filter(struct cgit_filter *filter, FILE *f, const char *prefix)
 {
 void cgit_fprintf_filter(struct cgit_filter *filter, FILE *f, const char *prefix)
 {

-       fprintf(f, "%s%s\n", prefix, filter->cmd);
+       filter->fprintf(filter, f, prefix);

 }
 
 }
 

+
+
+static const struct {
+       const char *prefix;
+       struct cgit_filter *(*ctor)(const char *cmd, int argument_count);
+} filter_specs[] = {
+       { "exec", new_exec_filter },
+};
+

 struct cgit_filter *cgit_new_filter(const char *cmd, filter_type filtertype)
 {
 struct cgit_filter *cgit_new_filter(const char *cmd, filter_type filtertype)
 {

-       struct cgit_filter *f;
-       int args_size = 0;
+       char *colon;
+       int i;
+       size_t len;
+       int argument_count;

 
        if (!cmd || !cmd[0])
                return NULL;
 
 
        if (!cmd || !cmd[0])
                return NULL;
 

-       f = xmalloc(sizeof(struct cgit_filter));
-       memset(f, 0, sizeof(struct cgit_filter));
+       colon = strchr(cmd, ':');
+       len = colon - cmd;
+       /*
+        * In case we're running on Windows, don't allow a single letter before
+        * the colon.
+        */
+       if (len == 1)
+               colon = NULL;

 
        switch (filtertype) {
                case SOURCE:
                case ABOUT:
 
        switch (filtertype) {
                case SOURCE:
                case ABOUT:

-                       f->extra_args = 1;
+                       argument_count = 1;

                        break;
 
                case COMMIT:
                default:
                        break;
 
                case COMMIT:
                default:

-                       f->extra_args = 0;
+                       argument_count = 0;

                        break;
        }
 
                        break;
        }
 

-       f->cmd = xstrdup(cmd);
-       args_size = (2 + f->extra_args) * sizeof(char *);
-       f->argv = xmalloc(args_size);
-       memset(f->argv, 0, args_size);
-       f->argv[0] = f->cmd;
-       return f;
+       /* If no prefix is given, exec filter is the default. */
+       if (!colon)
+               return new_exec_filter(cmd, argument_count);
+
+       for (i = 0; i < ARRAY_SIZE(filter_specs); i++) {
+               if (len == strlen(filter_specs[i].prefix) &&
+                   !strncmp(filter_specs[i].prefix, cmd, len))
+                       return filter_specs[i].ctor(colon + 1, argument_count);
+       }
+
+       die("Invalid filter type: %.*s", (int) len, cmd);

 }
 }