Figure 3–1 illustrates the XFN APIs that are used by the browser application.
The first example is a browser that lists all names that it finds in the namespace. When the program is invoked, the browser is set at the initial context or the composite name given on the command line.
See Commands and Sample Output.
/* * fnbrowse.c -- FNS namespace browser. * * To keep this example program relatively short, * limited error checking is done. */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <xfn/xfn.h> #define LINELEN 128 /* maximum length of input line */ typedef enum {CMD_DOWN, CMD_UP, CMD_LIST, CMD_SHOW, CMD_QUIT} command; static FN_status_t *status; static unsigned int auth = 0; /* non-authoritative */ /* Lookup a context named relative to the initial context. */ FN_ctx_t *lookup(const FN_composite_name_t *name); /* Set the browser's focus to the given context. */ void browse(FN_ctx_t *ctx); /* Set the browser's focus to a subcontext of the given context. */ void cmd_down(FN_ctx_t *ctx, const FN_composite_name_t *child); /* Print the names bound within a context. */ void cmd_list(FN_ctx_t *ctx); /* * Print a description of the reference bound to "child" in the * given context or, if "child" is the empty string, the reference * of the context itself. */ void cmd_show(FN_ctx_t *ctx, const FN_composite_name_t *child); /* * Read and parse the next command typed by the user. If the * command has an argument, set *argp to point to the argument. */ command read_command(FN_string_t **argp); /* Print an error message, and the description associated * with "status". */ void error(const char *msg); int main(int argc, char *argv[]) { unsigned char *target; switch (argc) { case 1: target = (unsigned char *)""; break; case 2: target = (unsigned char *)argv[1]; break; default: fprintf(stderr, "Usage: %s [<composite_name>]\n", argv[0]); return (1); } status = fn_status_create(); browse(lookup(fn_composite_name_from_str(target))); return (0); } FN_ctx_t * lookup(const FN_composite_name_t *name) { FN_ctx_t *ctx; FN_ref_t *ref; ctx = fn_ctx_handle_from_initial(auth, status); if (ctx == NULL) { error("Could not construct initial context"); exit(1); } if (fn_composite_name_is_empty(name)) { return (ctx); } ref = fn_ctx_lookup(ctx, name, status); fn_ctx_handle_destroy(ctx); if (ref == NULL) { error("Lookup failed"); exit(1); } ctx = fn_ctx_handle_from_ref(ref, auth, status); fn_ref_destroy(ref); if (ctx == NULL) { error("Could not construct context handle"); exit(1); } return (ctx); } void browse(FN_ctx_t *ctx) { FN_string_t *arg; FN_composite_name_t *child; while (1) { switch (read_command(&arg)) { case CMD_DOWN: child = fn_composite_name_from_string(arg); fn_string_destroy(arg); cmd_down(ctx, child); fn_composite_name_destroy(child); break; case CMD_UP: return; case CMD_LIST: cmd_list(ctx); break; case CMD_SHOW: child = fn_composite_name_from_string(arg); fn_string_destroy(arg); cmd_show(ctx, child); fn_composite_name_destroy(child); break; case CMD_QUIT: exit(0); } } } void cmd_down(FN_ctx_t *ctx, const FN_composite_name_t *child) { FN_ref_t *ref; FN_ctx_t *subctx; ref = fn_ctx_lookup(ctx, child, status); if (ref == NULL) { error("Lookup failed"); return; } subctx = fn_ctx_handle_from_ref(ref, auth, status); fn_ref_destroy(ref); if (subctx == NULL) { error("Could not construct context handle"); return; } browse(subctx); fn_ctx_handle_destroy(subctx); } void cmd_list(FN_ctx_t *ctx) { FN_string_t *empty_string = fn_string_create(); FN_composite_name_t *empty_name; FN_namelist_t *children; FN_string_t *child; unsigned intstatcode; int has_children = 0; empty_name = fn_composite_name_from_string(empty_string); fn_string_destroy(empty_string); children = fn_ctx_list_names(ctx, empty_name, status); fn_composite_name_destroy(empty_name); if (children == NULL) { error("Could not list names"); return; } while ((child = fn_namelist_next(children, status)) != NULL) { has_children = 1; printf("%s ", fn_string_str(child, &statcode)); fn_string_destroy(child); } if (has_children) { printf("\n"); } fn_namelist_destroy(children); } void cmd_show(FN_ctx_t *ctx, const FN_composite_name_t *child) { FN_string_t *desc; FN_ref_t *ref; unsigned int statcode; ref = fn_ctx_lookup(ctx, child, status); if (ref == NULL) { error("Lookup failed"); return; } desc = fn_ref_description(ref, 2, NULL); fn_ref_destroy(ref); if (desc != NULL) { printf("%s", fn_string_str(desc, &statcode)); fn_string_destroy(desc); } else { printf("[No description]\n"); } } command read_command(FN_string_t **argp) { char buf[LINELEN + 1]; char *cmd; char *child; while (printf("\n> "), fflush(stdout), gets(buf) != NULL) { cmd = strtok(buf, " \t"); if (cmd == NULL) { continue; } if (strcmp(cmd, "down") == 0) { child = strtok(NULL, " \t"); if (child != NULL) { *argp = fn_string_from_str((unsigned char *)child); return (CMD_DOWN); } } if (strcmp(cmd, "up") == 0) { return (CMD_UP); } if (strcmp(cmd, "list") == 0) { return (CMD_LIST); } if (strcmp(cmd, "show") == 0) { child = strtok(NULL, " \t"); *argp = (child != NULL) ? fn_string_from_str((unsigned char *)child) : fn_string_create(); return (CMD_SHOW); } if (strcmp(cmd, "quit") == 0) { return (CMD_QUIT); } fprintf(stderr, "Valid commands are: " "down <child>, up, list, show [<child>], quit\n"); } return (CMD_QUIT); /* EOF */ } void error(const char *msg) { FN_string_t *reason; unsigned int statcode; fprintf(stderr, "%s", msg); reason = fn_status_description(status, 0, NULL); if (reason != NULL) { fprintf(stderr, ": %s", (const char *)fn_string_str(reason, &statcode)); fn_string_destroy(reason); } fprintf(stderr, "\n"); } |
To compile Example 3–1, type:
% cc -o fnbrowse fnbrowse.c -lxfn |
To browse the namespace starting from the initial context, the program is invoked as:
% fnbrowse |
Or to browse a composite name and its descendents, type:
% fnbrowse composite_name |
The commands supported by the fnbrowse program are summarized in Table 3–1 .
Table 3–1 Namespace Browser Commands
Command |
Usage |
---|---|
down child |
Sets the browser at the subcontext of the child |
up |
Sets the browser at one level higher than the current context |
list |
Lists the names bound within the current context |
show |
Prints the reference of the current context |
show child |
Prints the reference of the current context's child |
quit |
Exits the browser |
Sample output for navigating the entire namespace is displayed here.
Note the following:
The first list command shows the initial context bindings.
The fnbrowse program lists all names it finds in the namespace, including names with underscores. These names are explained in Initial Context Bindings.
The three dots (...) represent the global namespace.
% fnbrowse > list _myorgunit ... _myself thishost myself _orgunit _host _thisens myens thisens org orgunit thisuser _thishost myorgunit _user thisorgunit host _thisorgunit _myens user |
Navigating the namespace is accomplished with the up and down commands. In the following output, the down command brings the focus of the browser to the enterprise root of the namespace, thisens (can also be myens). The show command displays information about the reference and address type for thisens.
> down thisens > show Reference type: onc_fn_enterprise Address type: on_fn_nisplus length: 20 context type: enterprise root representation: normal version: 0 internal name: eng.wiz.com > up > down thisorgunit |
Continuing with the example, this list command shows the contexts for thisorgunit.
> list service _fs _host _service _site site _user host fs user > down usr Lookup failed: Name Not Found: 'usr' > down service > list printer > down printer |
The list command shows the printer names that are bound in the printer context. The show command displays the reference for the child, colorful.
> list celeste _default color colorful quartz nuttree puffin > show colorful printer Reference type: onc_printers Address type: onc_printers_bsdaddr length: 12 data: 0x00 0x00 0x00 0x08 0x62 0x6c 0x61 0x63 0x6b 0x63 ....blackc 0x61 0x74 at > down colorful Could not construct context handle: No Supported Address > quit % |