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  1. /*
  2.  * Copyright (c) 2005 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup genericconsole
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file    kconsole.c
  35.  * @brief   Kernel console.
  36.  *
  37.  * This file contains kernel thread managing the kernel console.
  38.  */
  39.  
  40. #include <console/kconsole.h>
  41. #include <console/console.h>
  42. #include <console/chardev.h>
  43. #include <console/cmd.h>
  44. #include <print.h>
  45. #include <panic.h>
  46. #include <arch/types.h>
  47. #include <adt/list.h>
  48. #include <arch.h>
  49. #include <macros.h>
  50. #include <debug.h>
  51. #include <func.h>
  52. #include <string.h>
  53. #include <macros.h>
  54. #include <sysinfo/sysinfo.h>
  55. #include <ddi/device.h>
  56. #include <symtab.h>
  57. #include <errno.h>
  58.  
  59. /** Simple kernel console.
  60.  *
  61.  * The console is realized by kernel thread kconsole.
  62.  * It doesn't understand any useful command on its own,
  63.  * but makes it possible for other kernel subsystems to
  64.  * register their own commands.
  65.  */
  66.  
  67. /** Locking.
  68.  *
  69.  * There is a list of cmd_info_t structures. This list
  70.  * is protected by cmd_lock spinlock. Note that specially
  71.  * the link elements of cmd_info_t are protected by
  72.  * this lock.
  73.  *
  74.  * Each cmd_info_t also has its own lock, which protects
  75.  * all elements thereof except the link element.
  76.  *
  77.  * cmd_lock must be acquired before any cmd_info lock.
  78.  * When locking two cmd info structures, structure with
  79.  * lower address must be locked first.
  80.  */
  81.  
  82. SPINLOCK_INITIALIZE(cmd_lock);  /**< Lock protecting command list. */
  83. LIST_INITIALIZE(cmd_head);  /**< Command list. */
  84.  
  85. static cmd_info_t *parse_cmdline(char *cmdline, size_t len);
  86. static bool parse_argument(char *cmdline, size_t len, index_t *start,
  87.     index_t *end);
  88. static char history[KCONSOLE_HISTORY][MAX_CMDLINE] = {};
  89.  
  90. /*
  91.  * For now, we use 0 as INR.
  92.  * However, it is therefore desirable to have architecture specific
  93.  * definition of KCONSOLE_VIRT_INR in the future.
  94.  */
  95. #define KCONSOLE_VIRT_INR  0
  96.  
  97. bool kconsole_notify = false;
  98. irq_t kconsole_irq;
  99.  
  100.  
  101. /** Allways refuse IRQ ownership.
  102.  *
  103.  * This is not a real IRQ, so we always decline.
  104.  *
  105.  * @return Always returns IRQ_DECLINE.
  106.  *
  107.  */
  108. static irq_ownership_t kconsole_claim(irq_t *irq)
  109. {
  110.     return IRQ_DECLINE;
  111. }
  112.  
  113.  
  114. /** Initialize kconsole data structures
  115.  *
  116.  * This is the most basic initialization, almost no
  117.  * other kernel subsystem is ready yet.
  118.  *
  119.  */
  120. void kconsole_init(void)
  121. {
  122.     unsigned int i;
  123.  
  124.     cmd_init();
  125.     for (i = 0; i < KCONSOLE_HISTORY; i++)
  126.         history[i][0] = '\0';
  127. }
  128.  
  129.  
  130. /** Initialize kconsole notification mechanism
  131.  *
  132.  * Initialize the virtual IRQ notification mechanism.
  133.  *
  134.  */
  135. void kconsole_notify_init(void)
  136. {
  137.     sysinfo_set_item_val("kconsole.present", NULL, true);
  138.     sysinfo_set_item_val("kconsole.inr", NULL, KCONSOLE_VIRT_INR);
  139.    
  140.     irq_initialize(&kconsole_irq);
  141.     kconsole_irq.devno = device_assign_devno();
  142.     kconsole_irq.inr = KCONSOLE_VIRT_INR;
  143.     kconsole_irq.claim = kconsole_claim;
  144.     irq_register(&kconsole_irq);
  145.    
  146.     kconsole_notify = true;
  147. }
  148.  
  149.  
  150. /** Register kconsole command.
  151.  *
  152.  * @param cmd Structure describing the command.
  153.  *
  154.  * @return 0 on failure, 1 on success.
  155.  */
  156. int cmd_register(cmd_info_t *cmd)
  157. {
  158.     link_t *cur;
  159.    
  160.     spinlock_lock(&cmd_lock);
  161.    
  162.     /*
  163.      * Make sure the command is not already listed.
  164.      */
  165.     for (cur = cmd_head.next; cur != &cmd_head; cur = cur->next) {
  166.         cmd_info_t *hlp;
  167.        
  168.         hlp = list_get_instance(cur, cmd_info_t, link);
  169.  
  170.         if (hlp == cmd) {
  171.             /* The command is already there. */
  172.             spinlock_unlock(&cmd_lock);
  173.             return 0;
  174.         }
  175.  
  176.         /* Avoid deadlock. */
  177.         if (hlp < cmd) {
  178.             spinlock_lock(&hlp->lock);
  179.             spinlock_lock(&cmd->lock);
  180.         } else {
  181.             spinlock_lock(&cmd->lock);
  182.             spinlock_lock(&hlp->lock);
  183.         }
  184.         if ((strncmp(hlp->name, cmd->name, max(strlen(cmd->name),
  185.             strlen(hlp->name))) == 0)) {
  186.             /* The command is already there. */
  187.             spinlock_unlock(&hlp->lock);
  188.             spinlock_unlock(&cmd->lock);
  189.             spinlock_unlock(&cmd_lock);
  190.             return 0;
  191.         }
  192.        
  193.         spinlock_unlock(&hlp->lock);
  194.         spinlock_unlock(&cmd->lock);
  195.     }
  196.    
  197.     /*
  198.      * Now the command can be added.
  199.      */
  200.     list_append(&cmd->link, &cmd_head);
  201.    
  202.     spinlock_unlock(&cmd_lock);
  203.     return 1;
  204. }
  205.  
  206. /** Print count times a character */
  207. static void rdln_print_c(char ch, int count)
  208. {
  209.     int i;
  210.     for (i = 0; i < count; i++)
  211.         putchar(ch);
  212. }
  213.  
  214. /** Insert character to string */
  215. static void insert_char(char *str, char ch, int pos)
  216. {
  217.     int i;
  218.    
  219.     for (i = strlen(str); i > pos; i--)
  220.         str[i] = str[i - 1];
  221.     str[pos] = ch;
  222. }
  223.  
  224. /** Try to find a command beginning with prefix */
  225. static const char *cmdtab_search_one(const char *name,link_t **startpos)
  226. {
  227.     size_t namelen = strlen(name);
  228.     const char *curname;
  229.  
  230.     spinlock_lock(&cmd_lock);
  231.  
  232.     if (!*startpos)
  233.         *startpos = cmd_head.next;
  234.  
  235.     for (; *startpos != &cmd_head; *startpos = (*startpos)->next) {
  236.         cmd_info_t *hlp;
  237.         hlp = list_get_instance(*startpos, cmd_info_t, link);
  238.  
  239.         curname = hlp->name;
  240.         if (strlen(curname) < namelen)
  241.             continue;
  242.         if (strncmp(curname, name, namelen) == 0) {
  243.             spinlock_unlock(&cmd_lock);
  244.             return curname+namelen;
  245.         }
  246.     }
  247.     spinlock_unlock(&cmd_lock);
  248.     return NULL;
  249. }
  250.  
  251.  
  252. /** Command completion of the commands
  253.  *
  254.  * @param name - string to match, changed to hint on exit
  255.  * @return number of found matches
  256.  */
  257. static int cmdtab_compl(char *name)
  258. {
  259.     static char output[/*MAX_SYMBOL_NAME*/128 + 1];
  260.     link_t *startpos = NULL;
  261.     const char *foundtxt;
  262.     int found = 0;
  263.     int i;
  264.  
  265.     output[0] = '\0';
  266.     while ((foundtxt = cmdtab_search_one(name, &startpos))) {
  267.         startpos = startpos->next;
  268.         if (!found)
  269.             strncpy(output, foundtxt, strlen(foundtxt) + 1);
  270.         else {
  271.             for (i = 0; output[i] && foundtxt[i] &&
  272.                 output[i] == foundtxt[i]; i++)
  273.                 ;
  274.             output[i] = '\0';
  275.         }
  276.         found++;
  277.     }
  278.     if (!found)
  279.         return 0;
  280.  
  281.     if (found > 1 && !strlen(output)) {
  282.         printf("\n");
  283.         startpos = NULL;
  284.         while ((foundtxt = cmdtab_search_one(name, &startpos))) {
  285.             cmd_info_t *hlp;
  286.             hlp = list_get_instance(startpos, cmd_info_t, link);
  287.             printf("%s - %s\n", hlp->name, hlp->description);
  288.             startpos = startpos->next;
  289.         }
  290.     }
  291.     strncpy(name, output, 128/*MAX_SYMBOL_NAME*/);
  292.     return found;
  293. }
  294.  
  295. static char *clever_readline(const char *prompt, indev_t *input)
  296. {
  297.     static int histposition = 0;
  298.  
  299.     static char tmp[MAX_CMDLINE + 1];
  300.     int curlen = 0, position = 0;
  301.     char *current = history[histposition];
  302.     int i;
  303.     char mod; /* Command Modifier */
  304.     char c;
  305.  
  306.     printf("%s> ", prompt);
  307.     while (1) {
  308.         c = _getc(input);
  309.         if (c == '\n') {
  310.             putchar(c);
  311.             break;
  312.         }
  313.         if (c == '\b') { /* Backspace */
  314.             if (position == 0)
  315.                 continue;
  316.             for (i = position; i < curlen; i++)
  317.                 current[i - 1] = current[i];
  318.             curlen--;
  319.             position--;
  320.             putchar('\b');
  321.             for (i = position; i < curlen; i++)
  322.                 putchar(current[i]);
  323.             putchar(' ');
  324.             rdln_print_c('\b', curlen - position + 1);
  325.             continue;
  326.         }
  327.         if (c == '\t') { /* Tabulator */
  328.             int found;
  329.  
  330.             /* Move to the end of the word */
  331.             for (; position < curlen && current[position] != ' ';
  332.                 position++)
  333.                 putchar(current[position]);
  334.             /* Copy to tmp last word */
  335.             for (i = position - 1; i >= 0 && current[i] != ' '; i--)
  336.                 ;
  337.             /* If word begins with * or &, skip it */
  338.             if (tmp[0] == '*' || tmp[0] == '&')
  339.                 for (i = 1; tmp[i]; i++)
  340.                     tmp[i - 1] = tmp[i];
  341.             i++; /* I is at the start of the word */
  342.             strncpy(tmp, current + i, position - i + 1);
  343.  
  344.             if (i == 0) { /* Command completion */
  345.                 found = cmdtab_compl(tmp);
  346.             } else { /* Symtab completion */
  347.                 found = symtab_compl(tmp);
  348.             }
  349.  
  350.             if (found == 0)
  351.                 continue;
  352.             for (i = 0; tmp[i] && curlen < MAX_CMDLINE;
  353.                 i++, curlen++)
  354.                 insert_char(current, tmp[i], i + position);
  355.  
  356.             if (strlen(tmp) || found == 1) { /* If we have a hint */
  357.                 for (i = position; i < curlen; i++)
  358.                     putchar(current[i]);
  359.                 position += strlen(tmp);
  360.                 /* Add space to end */
  361.                 if (found == 1 && position == curlen &&
  362.                     curlen < MAX_CMDLINE) {
  363.                     current[position] = ' ';
  364.                     curlen++;
  365.                     position++;
  366.                     putchar(' ');
  367.                 }
  368.             } else { /* No hint, table was printed */
  369.                 printf("%s> ", prompt);
  370.                 for (i = 0; i < curlen; i++)
  371.                     putchar(current[i]);
  372.                 position += strlen(tmp);
  373.             }
  374.             rdln_print_c('\b', curlen - position);
  375.             continue;
  376.         }
  377.         if (c == 0x1b) { /* Special command */
  378.             mod = _getc(input);
  379.             c = _getc(input);
  380.  
  381.             if (mod != 0x5b && mod != 0x4f)
  382.                 continue;
  383.  
  384.             if (c == 0x33 && _getc(input) == 0x7e) {
  385.                 /* Delete */
  386.                 if (position == curlen)
  387.                     continue;
  388.                 for (i = position + 1; i < curlen; i++) {
  389.                     putchar(current[i]);
  390.                     current[i - 1] = current[i];
  391.                 }
  392.                 putchar(' ');
  393.                 rdln_print_c('\b', curlen - position);
  394.                 curlen--;
  395.             } else if (c == 0x48) { /* Home */
  396.                 rdln_print_c('\b', position);
  397.                 position = 0;
  398.             } else if (c == 0x46) {  /* End */
  399.                 for (i = position; i < curlen; i++)
  400.                     putchar(current[i]);
  401.                 position = curlen;
  402.             } else if (c == 0x44) { /* Left */
  403.                 if (position > 0) {
  404.                     putchar('\b');
  405.                     position--;
  406.                 }
  407.                 continue;
  408.             } else if (c == 0x43) { /* Right */
  409.                 if (position < curlen) {
  410.                     putchar(current[position]);
  411.                     position++;
  412.                 }
  413.                 continue;
  414.             } else if (c == 0x41 || c == 0x42) {
  415.                                 /* Up, down */
  416.                 rdln_print_c('\b', position);
  417.                 rdln_print_c(' ', curlen);
  418.                 rdln_print_c('\b', curlen);
  419.                 if (c == 0x41) /* Up */
  420.                     histposition--;
  421.                 else
  422.                     histposition++;
  423.                 if (histposition < 0) {
  424.                     histposition = KCONSOLE_HISTORY - 1;
  425.                 } else {
  426.                     histposition =
  427.                         histposition % KCONSOLE_HISTORY;
  428.                 }
  429.                 current = history[histposition];
  430.                 printf("%s", current);
  431.                 curlen = strlen(current);
  432.                 position = curlen;
  433.                 continue;
  434.             }
  435.             continue;
  436.         }
  437.         if (curlen >= MAX_CMDLINE)
  438.             continue;
  439.  
  440.         insert_char(current, c, position);
  441.  
  442.         curlen++;
  443.         for (i = position; i < curlen; i++)
  444.             putchar(current[i]);
  445.         position++;
  446.         rdln_print_c('\b',curlen - position);
  447.     }
  448.     if (curlen) {
  449.         histposition++;
  450.         histposition = histposition % KCONSOLE_HISTORY;
  451.     }
  452.     current[curlen] = '\0';
  453.     return current;
  454. }
  455.  
  456. bool kconsole_check_poll(void)
  457. {
  458.     return check_poll(stdin);
  459. }
  460.  
  461. /** Kernel console prompt.
  462.  *
  463.  * @param prompt Kernel console prompt (e.g kconsole/panic).
  464.  * @param msg    Message to display in the beginning.
  465.  * @param kcon   Wait for keypress to show the prompt
  466.  *               and never exit.
  467.  *
  468.  */
  469. void kconsole(char *prompt, char *msg, bool kcon)
  470. {
  471.     cmd_info_t *cmd_info;
  472.     count_t len;
  473.     char *cmdline;
  474.    
  475.     if (!stdin) {
  476.         LOG("No stdin for kernel console");
  477.         return;
  478.     }
  479.    
  480.     if (msg)
  481.         printf("%s", msg);
  482.    
  483.     if (kcon)
  484.         _getc(stdin);
  485.     else
  486.         printf("Type \"exit\" to leave the console.\n");
  487.    
  488.     while (true) {
  489.         cmdline = clever_readline((char *) prompt, stdin);
  490.         len = strlen(cmdline);
  491.         if (!len)
  492.             continue;
  493.        
  494.         if ((!kcon) && (len == 4) && (strncmp(cmdline, "exit", 4) == 0))
  495.             break;
  496.        
  497.         cmd_info = parse_cmdline(cmdline, len);
  498.         if (!cmd_info)
  499.             continue;
  500.        
  501.         (void) cmd_info->func(cmd_info->argv);
  502.     }
  503. }
  504.  
  505. /** Kernel console managing thread.
  506.  *
  507.  */
  508. void kconsole_thread(void *data)
  509. {
  510.     kconsole("kconsole", "Kernel console ready (press any key to activate)\n", true);
  511. }
  512.  
  513. static int parse_int_arg(char *text, size_t len, unative_t *result)
  514. {
  515.     uintptr_t symaddr;
  516.     bool isaddr = false;
  517.     bool isptr = false;
  518.     int rc;
  519.  
  520.     static char symname[MAX_SYMBOL_NAME];
  521.    
  522.     /* If we get a name, try to find it in symbol table */
  523.     if (text[0] == '&') {
  524.         isaddr = true;
  525.         text++;
  526.         len--;
  527.     } else if (text[0] == '*') {
  528.         isptr = true;
  529.         text++;
  530.         len--;
  531.     }
  532.     if (text[0] < '0' || text[0] > '9') {
  533.         strncpy(symname, text, min(len + 1, MAX_SYMBOL_NAME));
  534.         rc = symtab_addr_lookup(symname, &symaddr);
  535.         switch (rc) {
  536.         case ENOENT:
  537.             printf("Symbol %s not found.\n", symname);
  538.             return -1;
  539.         case EOVERFLOW:
  540.             printf("Duplicate symbol %s.\n", symname);
  541.             symtab_print_search(symname);
  542.             return -1;
  543.         default:
  544.             printf("No symbol information available.\n");
  545.             return -1;
  546.         }
  547.  
  548.         if (isaddr)
  549.             *result = (unative_t)symaddr;
  550.         else if (isptr)
  551.             *result = **((unative_t **)symaddr);
  552.         else
  553.             *result = *((unative_t *)symaddr);
  554.     } else { /* It's a number - convert it */
  555.         *result = atoi(text);
  556.         if (isptr)
  557.             *result = *((unative_t *)*result);
  558.     }
  559.  
  560.     return 0;
  561. }
  562.  
  563. /** Parse command line.
  564.  *
  565.  * @param cmdline Command line as read from input device.
  566.  * @param len Command line length.
  567.  *
  568.  * @return Structure describing the command.
  569.  */
  570. cmd_info_t *parse_cmdline(char *cmdline, size_t len)
  571. {
  572.     index_t start = 0, end = 0;
  573.     cmd_info_t *cmd = NULL;
  574.     link_t *cur;
  575.     count_t i;
  576.     int error = 0;
  577.    
  578.     if (!parse_argument(cmdline, len, &start, &end)) {
  579.         /* Command line did not contain alphanumeric word. */
  580.         return NULL;
  581.     }
  582.  
  583.     spinlock_lock(&cmd_lock);
  584.    
  585.     for (cur = cmd_head.next; cur != &cmd_head; cur = cur->next) {
  586.         cmd_info_t *hlp;
  587.        
  588.         hlp = list_get_instance(cur, cmd_info_t, link);
  589.         spinlock_lock(&hlp->lock);
  590.        
  591.         if (strncmp(hlp->name, &cmdline[start], max(strlen(hlp->name),
  592.             end - start + 1)) == 0) {
  593.             cmd = hlp;
  594.             break;
  595.         }
  596.        
  597.         spinlock_unlock(&hlp->lock);
  598.     }
  599.    
  600.     spinlock_unlock(&cmd_lock);
  601.    
  602.     if (!cmd) {
  603.         /* Unknown command. */
  604.         printf("Unknown command.\n");
  605.         return NULL;
  606.     }
  607.  
  608.     /* cmd == hlp is locked */
  609.    
  610.     /*
  611.      * The command line must be further analyzed and
  612.      * the parameters therefrom must be matched and
  613.      * converted to those specified in the cmd info
  614.      * structure.
  615.      */
  616.  
  617.     for (i = 0; i < cmd->argc; i++) {
  618.         char *buf;
  619.         start = end + 1;
  620.         if (!parse_argument(cmdline, len, &start, &end)) {
  621.             printf("Too few arguments.\n");
  622.             spinlock_unlock(&cmd->lock);
  623.             return NULL;
  624.         }
  625.        
  626.         error = 0;
  627.         switch (cmd->argv[i].type) {
  628.         case ARG_TYPE_STRING:
  629.             buf = (char *) cmd->argv[i].buffer;
  630.             strncpy(buf, (const char *) &cmdline[start],
  631.                 min((end - start) + 2, cmd->argv[i].len));
  632.             buf[min((end - start) + 1, cmd->argv[i].len - 1)] =
  633.                 '\0';
  634.             break;
  635.         case ARG_TYPE_INT:
  636.             if (parse_int_arg(cmdline + start, end - start + 1,
  637.                 &cmd->argv[i].intval))
  638.                 error = 1;
  639.             break;
  640.         case ARG_TYPE_VAR:
  641.             if (start != end && cmdline[start] == '"' &&
  642.                 cmdline[end] == '"') {
  643.                 buf = (char *) cmd->argv[i].buffer;
  644.                 strncpy(buf, (const char *) &cmdline[start + 1],
  645.                     min((end-start), cmd->argv[i].len));
  646.                 buf[min((end - start), cmd->argv[i].len - 1)] =
  647.                     '\0';
  648.                 cmd->argv[i].intval = (unative_t) buf;
  649.                 cmd->argv[i].vartype = ARG_TYPE_STRING;
  650.             } else if (!parse_int_arg(cmdline + start,
  651.                 end - start + 1, &cmd->argv[i].intval)) {
  652.                 cmd->argv[i].vartype = ARG_TYPE_INT;
  653.             } else {
  654.                 printf("Unrecognized variable argument.\n");
  655.                 error = 1;
  656.             }
  657.             break;
  658.         case ARG_TYPE_INVALID:
  659.         default:
  660.             printf("invalid argument type\n");
  661.             error = 1;
  662.             break;
  663.         }
  664.     }
  665.    
  666.     if (error) {
  667.         spinlock_unlock(&cmd->lock);
  668.         return NULL;
  669.     }
  670.    
  671.     start = end + 1;
  672.     if (parse_argument(cmdline, len, &start, &end)) {
  673.         printf("Too many arguments.\n");
  674.         spinlock_unlock(&cmd->lock);
  675.         return NULL;
  676.     }
  677.    
  678.     spinlock_unlock(&cmd->lock);
  679.     return cmd;
  680. }
  681.  
  682. /** Parse argument.
  683.  *
  684.  * Find start and end positions of command line argument.
  685.  *
  686.  * @param cmdline Command line as read from the input device.
  687.  * @param len Number of characters in cmdline.
  688.  * @param start On entry, 'start' contains pointer to the index
  689.  *        of first unprocessed character of cmdline.
  690.  *        On successful exit, it marks beginning of the next argument.
  691.  * @param end Undefined on entry. On exit, 'end' points to the last character
  692.  *        of the next argument.
  693.  *
  694.  * @return false on failure, true on success.
  695.  */
  696. bool parse_argument(char *cmdline, size_t len, index_t *start, index_t *end)
  697. {
  698.     index_t i;
  699.     bool found_start = false;
  700.    
  701.     ASSERT(start != NULL);
  702.     ASSERT(end != NULL);
  703.    
  704.     for (i = *start; i < len; i++) {
  705.         if (!found_start) {
  706.             if (isspace(cmdline[i]))
  707.                 (*start)++;
  708.             else
  709.                 found_start = true;
  710.         } else {
  711.             if (isspace(cmdline[i]))
  712.                 break;
  713.         }
  714.     }
  715.     *end = i - 1;
  716.  
  717.     return found_start;
  718. }
  719.  
  720. /** @}
  721.  */
  722.