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  1. /*
  2.  * Copyright (c) 2008 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 fs
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file    fat_ops.c
  35.  * @brief   Implementation of VFS operations for the FAT file system server.
  36.  */
  37.  
  38. #include "fat.h"
  39. #include "fat_dentry.h"
  40. #include "fat_fat.h"
  41. #include "../../vfs/vfs.h"
  42. #include <libfs.h>
  43. #include <libblock.h>
  44. #include <ipc/ipc.h>
  45. #include <ipc/services.h>
  46. #include <ipc/devmap.h>
  47. #include <async.h>
  48. #include <errno.h>
  49. #include <string.h>
  50. #include <byteorder.h>
  51. #include <libadt/hash_table.h>
  52. #include <libadt/list.h>
  53. #include <assert.h>
  54. #include <futex.h>
  55. #include <sys/mman.h>
  56. #include <align.h>
  57.  
  58. /** Futex protecting the list of cached free FAT nodes. */
  59. static futex_t ffn_futex = FUTEX_INITIALIZER;
  60.  
  61. /** List of cached free FAT nodes. */
  62. static LIST_INITIALIZE(ffn_head);
  63.  
  64. static void fat_node_initialize(fat_node_t *node)
  65. {
  66.     futex_initialize(&node->lock, 1);
  67.     node->idx = NULL;
  68.     node->type = 0;
  69.     link_initialize(&node->ffn_link);
  70.     node->size = 0;
  71.     node->lnkcnt = 0;
  72.     node->refcnt = 0;
  73.     node->dirty = false;
  74. }
  75.  
  76. static void fat_node_sync(fat_node_t *node)
  77. {
  78.     block_t *b;
  79.     fat_bs_t *bs;
  80.     fat_dentry_t *d;
  81.     uint16_t bps;
  82.     unsigned dps;
  83.    
  84.     assert(node->dirty);
  85.  
  86.     bs = block_bb_get(node->idx->dev_handle);
  87.     bps = uint16_t_le2host(bs->bps);
  88.     dps = bps / sizeof(fat_dentry_t);
  89.    
  90.     /* Read the block that contains the dentry of interest. */
  91.     b = _fat_block_get(bs, node->idx->dev_handle, node->idx->pfc,
  92.         (node->idx->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);
  93.  
  94.     d = ((fat_dentry_t *)b->data) + (node->idx->pdi % dps);
  95.  
  96.     d->firstc = host2uint16_t_le(node->firstc);
  97.     if (node->type == FAT_FILE)
  98.         d->size = host2uint32_t_le(node->size);
  99.     /* TODO: update other fields? (e.g time fields, attr field) */
  100.    
  101.     b->dirty = true;        /* need to sync block */
  102.     block_put(b);
  103. }
  104.  
  105. static fat_node_t *fat_node_get_new(void)
  106. {
  107.     fat_node_t *nodep;
  108.  
  109.     futex_down(&ffn_futex);
  110.     if (!list_empty(&ffn_head)) {
  111.         /* Try to use a cached free node structure. */
  112.         fat_idx_t *idxp_tmp;
  113.         nodep = list_get_instance(ffn_head.next, fat_node_t, ffn_link);
  114.         if (futex_trydown(&nodep->lock) == ESYNCH_WOULD_BLOCK)
  115.             goto skip_cache;
  116.         idxp_tmp = nodep->idx;
  117.         if (futex_trydown(&idxp_tmp->lock) == ESYNCH_WOULD_BLOCK) {
  118.             futex_up(&nodep->lock);
  119.             goto skip_cache;
  120.         }
  121.         list_remove(&nodep->ffn_link);
  122.         futex_up(&ffn_futex);
  123.         if (nodep->dirty)
  124.             fat_node_sync(nodep);
  125.         idxp_tmp->nodep = NULL;
  126.         futex_up(&nodep->lock);
  127.         futex_up(&idxp_tmp->lock);
  128.     } else {
  129. skip_cache:
  130.         /* Try to allocate a new node structure. */
  131.         futex_up(&ffn_futex);
  132.         nodep = (fat_node_t *)malloc(sizeof(fat_node_t));
  133.         if (!nodep)
  134.             return NULL;
  135.     }
  136.     fat_node_initialize(nodep);
  137.    
  138.     return nodep;
  139. }
  140.  
  141. /** Internal version of fat_node_get().
  142.  *
  143.  * @param idxp      Locked index structure.
  144.  */
  145. static void *fat_node_get_core(fat_idx_t *idxp)
  146. {
  147.     block_t *b;
  148.     fat_bs_t *bs;
  149.     fat_dentry_t *d;
  150.     fat_node_t *nodep = NULL;
  151.     unsigned bps;
  152.     unsigned spc;
  153.     unsigned dps;
  154.  
  155.     if (idxp->nodep) {
  156.         /*
  157.          * We are lucky.
  158.          * The node is already instantiated in memory.
  159.          */
  160.         futex_down(&idxp->nodep->lock);
  161.         if (!idxp->nodep->refcnt++)
  162.             list_remove(&idxp->nodep->ffn_link);
  163.         futex_up(&idxp->nodep->lock);
  164.         return idxp->nodep;
  165.     }
  166.  
  167.     /*
  168.      * We must instantiate the node from the file system.
  169.      */
  170.    
  171.     assert(idxp->pfc);
  172.  
  173.     nodep = fat_node_get_new();
  174.     if (!nodep)
  175.         return NULL;
  176.  
  177.     bs = block_bb_get(idxp->dev_handle);
  178.     bps = uint16_t_le2host(bs->bps);
  179.     spc = bs->spc;
  180.     dps = bps / sizeof(fat_dentry_t);
  181.  
  182.     /* Read the block that contains the dentry of interest. */
  183.     b = _fat_block_get(bs, idxp->dev_handle, idxp->pfc,
  184.         (idxp->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);
  185.     assert(b);
  186.  
  187.     d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);
  188.     if (d->attr & FAT_ATTR_SUBDIR) {
  189.         /*
  190.          * The only directory which does not have this bit set is the
  191.          * root directory itself. The root directory node is handled
  192.          * and initialized elsewhere.
  193.          */
  194.         nodep->type = FAT_DIRECTORY;
  195.         /*
  196.          * Unfortunately, the 'size' field of the FAT dentry is not
  197.          * defined for the directory entry type. We must determine the
  198.          * size of the directory by walking the FAT.
  199.          */
  200.         nodep->size = bps * spc * fat_clusters_get(bs, idxp->dev_handle,
  201.             uint16_t_le2host(d->firstc));
  202.     } else {
  203.         nodep->type = FAT_FILE;
  204.         nodep->size = uint32_t_le2host(d->size);
  205.     }
  206.     nodep->firstc = uint16_t_le2host(d->firstc);
  207.     nodep->lnkcnt = 1;
  208.     nodep->refcnt = 1;
  209.  
  210.     block_put(b);
  211.  
  212.     /* Link the idx structure with the node structure. */
  213.     nodep->idx = idxp;
  214.     idxp->nodep = nodep;
  215.  
  216.     return nodep;
  217. }
  218.  
  219. /*
  220.  * Forward declarations of FAT libfs operations.
  221.  */
  222. static void *fat_node_get(dev_handle_t, fs_index_t);
  223. static void fat_node_put(void *);
  224. static void *fat_create_node(dev_handle_t, int);
  225. static int fat_destroy_node(void *);
  226. static int fat_link(void *, void *, const char *);
  227. static int fat_unlink(void *, void *);
  228. static void *fat_match(void *, const char *);
  229. static fs_index_t fat_index_get(void *);
  230. static size_t fat_size_get(void *);
  231. static unsigned fat_lnkcnt_get(void *);
  232. static bool fat_has_children(void *);
  233. static void *fat_root_get(dev_handle_t);
  234. static char fat_plb_get_char(unsigned);
  235. static bool fat_is_directory(void *);
  236. static bool fat_is_file(void *node);
  237.  
  238. /*
  239.  * FAT libfs operations.
  240.  */
  241.  
  242. /** Instantiate a FAT in-core node. */
  243. void *fat_node_get(dev_handle_t dev_handle, fs_index_t index)
  244. {
  245.     void *node;
  246.     fat_idx_t *idxp;
  247.  
  248.     idxp = fat_idx_get_by_index(dev_handle, index);
  249.     if (!idxp)
  250.         return NULL;
  251.     /* idxp->lock held */
  252.     node = fat_node_get_core(idxp);
  253.     futex_up(&idxp->lock);
  254.     return node;
  255. }
  256.  
  257. void fat_node_put(void *node)
  258. {
  259.     fat_node_t *nodep = (fat_node_t *)node;
  260.     bool destroy = false;
  261.  
  262.     futex_down(&nodep->lock);
  263.     if (!--nodep->refcnt) {
  264.         if (nodep->idx) {
  265.             futex_down(&ffn_futex);
  266.             list_append(&nodep->ffn_link, &ffn_head);
  267.             futex_up(&ffn_futex);
  268.         } else {
  269.             /*
  270.              * The node does not have any index structure associated
  271.              * with itself. This can only mean that we are releasing
  272.              * the node after a failed attempt to allocate the index
  273.              * structure for it.
  274.              */
  275.             destroy = true;
  276.         }
  277.     }
  278.     futex_up(&nodep->lock);
  279.     if (destroy)
  280.         free(node);
  281. }
  282.  
  283. void *fat_create_node(dev_handle_t dev_handle, int flags)
  284. {
  285.     fat_idx_t *idxp;
  286.     fat_node_t *nodep;
  287.  
  288.     nodep = fat_node_get_new();
  289.     if (!nodep)
  290.         return NULL;
  291.     idxp = fat_idx_get_new(dev_handle);
  292.     if (!idxp) {
  293.         fat_node_put(nodep);
  294.         return NULL;
  295.     }
  296.     /* idxp->lock held */
  297.     if (flags & L_DIRECTORY) {
  298.         nodep->type = FAT_DIRECTORY;
  299.     } else {
  300.         nodep->type = FAT_FILE;
  301.     }
  302.     nodep->size = 0;
  303.     nodep->firstc = FAT_CLST_RES0;
  304.     nodep->lnkcnt = 0;  /* not linked anywhere */
  305.     nodep->refcnt = 1;
  306.  
  307.     nodep->idx = idxp;
  308.     idxp->nodep = nodep;
  309.  
  310.     futex_up(&idxp->lock);
  311.     return nodep;
  312. }
  313.  
  314. int fat_destroy_node(void *node)
  315. {
  316.     fat_node_t *nodep = (fat_node_t *)node;
  317.     fat_bs_t *bs;
  318.  
  319.     /*
  320.      * The node is not reachable from the file system. This means that the
  321.      * link count should be zero and that the index structure cannot be
  322.      * found in the position hash. Obviously, we don't need to lock the node
  323.      * nor its index structure.
  324.      */
  325.     assert(nodep->lnkcnt == 0);
  326.  
  327.     /*
  328.      * The node may not have any children.
  329.      */
  330.     assert(fat_has_children(node) == false);
  331.  
  332.     bs = block_bb_get(nodep->idx->dev_handle);
  333.     if (nodep->firstc != FAT_CLST_RES0) {
  334.         assert(nodep->size);
  335.         /* Free all clusters allocated to the node. */
  336.         fat_free_clusters(bs, nodep->idx->dev_handle, nodep->firstc);
  337.     }
  338.  
  339.     fat_idx_destroy(nodep->idx);
  340.     free(nodep);
  341.     return EOK;
  342. }
  343.  
  344. int fat_link(void *prnt, void *chld, const char *name)
  345. {
  346.     return ENOTSUP; /* not supported at the moment */
  347. }
  348.  
  349. int fat_unlink(void *prnt, void *chld)
  350. {
  351.     return ENOTSUP; /* not supported at the moment */
  352. }
  353.  
  354. void *fat_match(void *prnt, const char *component)
  355. {
  356.     fat_bs_t *bs;
  357.     fat_node_t *parentp = (fat_node_t *)prnt;
  358.     char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  359.     unsigned i, j;
  360.     unsigned bps;       /* bytes per sector */
  361.     unsigned dps;       /* dentries per sector */
  362.     unsigned blocks;
  363.     fat_dentry_t *d;
  364.     block_t *b;
  365.  
  366.     futex_down(&parentp->idx->lock);
  367.     bs = block_bb_get(parentp->idx->dev_handle);
  368.     bps = uint16_t_le2host(bs->bps);
  369.     dps = bps / sizeof(fat_dentry_t);
  370.     blocks = parentp->size / bps;
  371.     for (i = 0; i < blocks; i++) {
  372.         b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NONE);
  373.         for (j = 0; j < dps; j++) {
  374.             d = ((fat_dentry_t *)b->data) + j;
  375.             switch (fat_classify_dentry(d)) {
  376.             case FAT_DENTRY_SKIP:
  377.                 continue;
  378.             case FAT_DENTRY_LAST:
  379.                 block_put(b);
  380.                 futex_up(&parentp->idx->lock);
  381.                 return NULL;
  382.             default:
  383.             case FAT_DENTRY_VALID:
  384.                 dentry_name_canonify(d, name);
  385.                 break;
  386.             }
  387.             if (stricmp(name, component) == 0) {
  388.                 /* hit */
  389.                 void *node;
  390.                 /*
  391.                  * Assume tree hierarchy for locking.  We
  392.                  * already have the parent and now we are going
  393.                  * to lock the child.  Never lock in the oposite
  394.                  * order.
  395.                  */
  396.                 fat_idx_t *idx = fat_idx_get_by_pos(
  397.                     parentp->idx->dev_handle, parentp->firstc,
  398.                     i * dps + j);
  399.                 futex_up(&parentp->idx->lock);
  400.                 if (!idx) {
  401.                     /*
  402.                      * Can happen if memory is low or if we
  403.                      * run out of 32-bit indices.
  404.                      */
  405.                     block_put(b);
  406.                     return NULL;
  407.                 }
  408.                 node = fat_node_get_core(idx);
  409.                 futex_up(&idx->lock);
  410.                 block_put(b);
  411.                 return node;
  412.             }
  413.         }
  414.         block_put(b);
  415.     }
  416.  
  417.     futex_up(&parentp->idx->lock);
  418.     return NULL;
  419. }
  420.  
  421. fs_index_t fat_index_get(void *node)
  422. {
  423.     fat_node_t *fnodep = (fat_node_t *)node;
  424.     if (!fnodep)
  425.         return 0;
  426.     return fnodep->idx->index;
  427. }
  428.  
  429. size_t fat_size_get(void *node)
  430. {
  431.     return ((fat_node_t *)node)->size;
  432. }
  433.  
  434. unsigned fat_lnkcnt_get(void *node)
  435. {
  436.     return ((fat_node_t *)node)->lnkcnt;
  437. }
  438.  
  439. bool fat_has_children(void *node)
  440. {
  441.     fat_bs_t *bs;
  442.     fat_node_t *nodep = (fat_node_t *)node;
  443.     unsigned bps;
  444.     unsigned dps;
  445.     unsigned blocks;
  446.     block_t *b;
  447.     unsigned i, j;
  448.  
  449.     if (nodep->type != FAT_DIRECTORY)
  450.         return false;
  451.    
  452.     futex_down(&nodep->idx->lock);
  453.     bs = block_bb_get(nodep->idx->dev_handle);
  454.     bps = uint16_t_le2host(bs->bps);
  455.     dps = bps / sizeof(fat_dentry_t);
  456.  
  457.     blocks = nodep->size / bps;
  458.  
  459.     for (i = 0; i < blocks; i++) {
  460.         fat_dentry_t *d;
  461.    
  462.         b = fat_block_get(bs, nodep, i, BLOCK_FLAGS_NONE);
  463.         for (j = 0; j < dps; j++) {
  464.             d = ((fat_dentry_t *)b->data) + j;
  465.             switch (fat_classify_dentry(d)) {
  466.             case FAT_DENTRY_SKIP:
  467.                 continue;
  468.             case FAT_DENTRY_LAST:
  469.                 block_put(b);
  470.                 futex_up(&nodep->idx->lock);
  471.                 return false;
  472.             default:
  473.             case FAT_DENTRY_VALID:
  474.                 block_put(b);
  475.                 futex_up(&nodep->idx->lock);
  476.                 return true;
  477.             }
  478.             block_put(b);
  479.             futex_up(&nodep->idx->lock);
  480.             return true;
  481.         }
  482.         block_put(b);
  483.     }
  484.  
  485.     futex_up(&nodep->idx->lock);
  486.     return false;
  487. }
  488.  
  489. void *fat_root_get(dev_handle_t dev_handle)
  490. {
  491.     return fat_node_get(dev_handle, 0);
  492. }
  493.  
  494. char fat_plb_get_char(unsigned pos)
  495. {
  496.     return fat_reg.plb_ro[pos % PLB_SIZE];
  497. }
  498.  
  499. bool fat_is_directory(void *node)
  500. {
  501.     return ((fat_node_t *)node)->type == FAT_DIRECTORY;
  502. }
  503.  
  504. bool fat_is_file(void *node)
  505. {
  506.     return ((fat_node_t *)node)->type == FAT_FILE;
  507. }
  508.  
  509. /** libfs operations */
  510. libfs_ops_t fat_libfs_ops = {
  511.     .match = fat_match,
  512.     .node_get = fat_node_get,
  513.     .node_put = fat_node_put,
  514.     .create = fat_create_node,
  515.     .destroy = fat_destroy_node,
  516.     .link = fat_link,
  517.     .unlink = fat_unlink,
  518.     .index_get = fat_index_get,
  519.     .size_get = fat_size_get,
  520.     .lnkcnt_get = fat_lnkcnt_get,
  521.     .has_children = fat_has_children,
  522.     .root_get = fat_root_get,
  523.     .plb_get_char = fat_plb_get_char,
  524.     .is_directory = fat_is_directory,
  525.     .is_file = fat_is_file
  526. };
  527.  
  528. /*
  529.  * VFS operations.
  530.  */
  531.  
  532. void fat_mounted(ipc_callid_t rid, ipc_call_t *request)
  533. {
  534.     dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  535.     fat_bs_t *bs;
  536.     uint16_t bps;
  537.     uint16_t rde;
  538.     int rc;
  539.  
  540.     /* initialize libblock */
  541.     rc = block_init(dev_handle, BS_SIZE);
  542.     if (rc != EOK) {
  543.         ipc_answer_0(rid, rc);
  544.         return;
  545.     }
  546.  
  547.     /* prepare the boot block */
  548.     rc = block_bb_read(dev_handle, BS_BLOCK * BS_SIZE, BS_SIZE);
  549.     if (rc != EOK) {
  550.         block_fini(dev_handle);
  551.         ipc_answer_0(rid, rc);
  552.         return;
  553.     }
  554.  
  555.     /* get the buffer with the boot sector */
  556.     bs = block_bb_get(dev_handle);
  557.    
  558.     /* Read the number of root directory entries. */
  559.     bps = uint16_t_le2host(bs->bps);
  560.     rde = uint16_t_le2host(bs->root_ent_max);
  561.  
  562.     if (bps != BS_SIZE) {
  563.         block_fini(dev_handle);
  564.         ipc_answer_0(rid, ENOTSUP);
  565.         return;
  566.     }
  567.  
  568.     /* Initialize the block cache */
  569.     rc = block_cache_init(dev_handle, bps, 0 /* XXX */);
  570.     if (rc != EOK) {
  571.         block_fini(dev_handle);
  572.         ipc_answer_0(rid, rc);
  573.         return;
  574.     }
  575.  
  576.     rc = fat_idx_init_by_dev_handle(dev_handle);
  577.     if (rc != EOK) {
  578.         block_fini(dev_handle);
  579.         ipc_answer_0(rid, rc);
  580.         return;
  581.     }
  582.  
  583.     /* Initialize the root node. */
  584.     fat_node_t *rootp = (fat_node_t *)malloc(sizeof(fat_node_t));
  585.     if (!rootp) {
  586.         block_fini(dev_handle);
  587.         fat_idx_fini_by_dev_handle(dev_handle);
  588.         ipc_answer_0(rid, ENOMEM);
  589.         return;
  590.     }
  591.     fat_node_initialize(rootp);
  592.  
  593.     fat_idx_t *ridxp = fat_idx_get_by_pos(dev_handle, FAT_CLST_ROOTPAR, 0);
  594.     if (!ridxp) {
  595.         block_fini(dev_handle);
  596.         free(rootp);
  597.         fat_idx_fini_by_dev_handle(dev_handle);
  598.         ipc_answer_0(rid, ENOMEM);
  599.         return;
  600.     }
  601.     assert(ridxp->index == 0);
  602.     /* ridxp->lock held */
  603.  
  604.     rootp->type = FAT_DIRECTORY;
  605.     rootp->firstc = FAT_CLST_ROOT;
  606.     rootp->refcnt = 1;
  607.     rootp->lnkcnt = 0;  /* FS root is not linked */
  608.     rootp->size = rde * sizeof(fat_dentry_t);
  609.     rootp->idx = ridxp;
  610.     ridxp->nodep = rootp;
  611.    
  612.     futex_up(&ridxp->lock);
  613.  
  614.     ipc_answer_3(rid, EOK, ridxp->index, rootp->size, rootp->lnkcnt);
  615. }
  616.  
  617. void fat_mount(ipc_callid_t rid, ipc_call_t *request)
  618. {
  619.     ipc_answer_0(rid, ENOTSUP);
  620. }
  621.  
  622. void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
  623. {
  624.     libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
  625. }
  626.  
  627. void fat_read(ipc_callid_t rid, ipc_call_t *request)
  628. {
  629.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  630.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  631.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  632.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  633.     fat_bs_t *bs;
  634.     uint16_t bps;
  635.     size_t bytes;
  636.     block_t *b;
  637.  
  638.     if (!nodep) {
  639.         ipc_answer_0(rid, ENOENT);
  640.         return;
  641.     }
  642.  
  643.     ipc_callid_t callid;
  644.     size_t len;
  645.     if (!ipc_data_read_receive(&callid, &len)) {
  646.         fat_node_put(nodep);
  647.         ipc_answer_0(callid, EINVAL);
  648.         ipc_answer_0(rid, EINVAL);
  649.         return;
  650.     }
  651.  
  652.     bs = block_bb_get(dev_handle);
  653.     bps = uint16_t_le2host(bs->bps);
  654.  
  655.     if (nodep->type == FAT_FILE) {
  656.         /*
  657.          * Our strategy for regular file reads is to read one block at
  658.          * most and make use of the possibility to return less data than
  659.          * requested. This keeps the code very simple.
  660.          */
  661.         if (pos >= nodep->size) {
  662.             /* reading beyond the EOF */
  663.             bytes = 0;
  664.             (void) ipc_data_read_finalize(callid, NULL, 0);
  665.         } else {
  666.             bytes = min(len, bps - pos % bps);
  667.             bytes = min(bytes, nodep->size - pos);
  668.             b = fat_block_get(bs, nodep, pos / bps,
  669.                 BLOCK_FLAGS_NONE);
  670.             (void) ipc_data_read_finalize(callid, b->data + pos % bps,
  671.                 bytes);
  672.             block_put(b);
  673.         }
  674.     } else {
  675.         unsigned bnum;
  676.         off_t spos = pos;
  677.         char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  678.         fat_dentry_t *d;
  679.  
  680.         assert(nodep->type == FAT_DIRECTORY);
  681.         assert(nodep->size % bps == 0);
  682.         assert(bps % sizeof(fat_dentry_t) == 0);
  683.  
  684.         /*
  685.          * Our strategy for readdir() is to use the position pointer as
  686.          * an index into the array of all dentries. On entry, it points
  687.          * to the first unread dentry. If we skip any dentries, we bump
  688.          * the position pointer accordingly.
  689.          */
  690.         bnum = (pos * sizeof(fat_dentry_t)) / bps;
  691.         while (bnum < nodep->size / bps) {
  692.             off_t o;
  693.  
  694.             b = fat_block_get(bs, nodep, bnum, BLOCK_FLAGS_NONE);
  695.             for (o = pos % (bps / sizeof(fat_dentry_t));
  696.                 o < bps / sizeof(fat_dentry_t);
  697.                 o++, pos++) {
  698.                 d = ((fat_dentry_t *)b->data) + o;
  699.                 switch (fat_classify_dentry(d)) {
  700.                 case FAT_DENTRY_SKIP:
  701.                     continue;
  702.                 case FAT_DENTRY_LAST:
  703.                     block_put(b);
  704.                     goto miss;
  705.                 default:
  706.                 case FAT_DENTRY_VALID:
  707.                     dentry_name_canonify(d, name);
  708.                     block_put(b);
  709.                     goto hit;
  710.                 }
  711.             }
  712.             block_put(b);
  713.             bnum++;
  714.         }
  715. miss:
  716.         fat_node_put(nodep);
  717.         ipc_answer_0(callid, ENOENT);
  718.         ipc_answer_1(rid, ENOENT, 0);
  719.         return;
  720. hit:
  721.         (void) ipc_data_read_finalize(callid, name, strlen(name) + 1);
  722.         bytes = (pos - spos) + 1;
  723.     }
  724.  
  725.     fat_node_put(nodep);
  726.     ipc_answer_1(rid, EOK, (ipcarg_t)bytes);
  727. }
  728.  
  729. void fat_write(ipc_callid_t rid, ipc_call_t *request)
  730. {
  731.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  732.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  733.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  734.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  735.     fat_bs_t *bs;
  736.     size_t bytes;
  737.     block_t *b;
  738.     uint16_t bps;
  739.     unsigned spc;
  740.     unsigned bpc;       /* bytes per cluster */
  741.     off_t boundary;
  742.     int flags = BLOCK_FLAGS_NONE;
  743.    
  744.     if (!nodep) {
  745.         ipc_answer_0(rid, ENOENT);
  746.         return;
  747.     }
  748.    
  749.     ipc_callid_t callid;
  750.     size_t len;
  751.     if (!ipc_data_write_receive(&callid, &len)) {
  752.         fat_node_put(nodep);
  753.         ipc_answer_0(callid, EINVAL);
  754.         ipc_answer_0(rid, EINVAL);
  755.         return;
  756.     }
  757.  
  758.     bs = block_bb_get(dev_handle);
  759.     bps = uint16_t_le2host(bs->bps);
  760.     spc = bs->spc;
  761.     bpc = bps * spc;
  762.  
  763.     /*
  764.      * In all scenarios, we will attempt to write out only one block worth
  765.      * of data at maximum. There might be some more efficient approaches,
  766.      * but this one greatly simplifies fat_write(). Note that we can afford
  767.      * to do this because the client must be ready to handle the return
  768.      * value signalizing a smaller number of bytes written.
  769.      */
  770.     bytes = min(len, bps - pos % bps);
  771.     if (bytes == bps)
  772.         flags |= BLOCK_FLAGS_NOREAD;
  773.    
  774.     boundary = ROUND_UP(nodep->size, bpc);
  775.     if (pos < boundary) {
  776.         /*
  777.          * This is the easier case - we are either overwriting already
  778.          * existing contents or writing behind the EOF, but still within
  779.          * the limits of the last cluster. The node size may grow to the
  780.          * next block size boundary.
  781.          */
  782.         fat_fill_gap(bs, nodep, FAT_CLST_RES0, pos);
  783.         b = fat_block_get(bs, nodep, pos / bps, flags);
  784.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  785.             bytes);
  786.         b->dirty = true;        /* need to sync block */
  787.         block_put(b);
  788.         if (pos + bytes > nodep->size) {
  789.             nodep->size = pos + bytes;
  790.             nodep->dirty = true;    /* need to sync node */
  791.         }
  792.         ipc_answer_2(rid, EOK, bytes, nodep->size);
  793.         fat_node_put(nodep);
  794.         return;
  795.     } else {
  796.         /*
  797.          * This is the more difficult case. We must allocate new
  798.          * clusters for the node and zero them out.
  799.          */
  800.         int status;
  801.         unsigned nclsts;
  802.         fat_cluster_t mcl, lcl;
  803.  
  804.         nclsts = (ROUND_UP(pos + bytes, bpc) - boundary) / bpc;
  805.         /* create an independent chain of nclsts clusters in all FATs */
  806.         status = fat_alloc_clusters(bs, dev_handle, nclsts, &mcl, &lcl);
  807.         if (status != EOK) {
  808.             /* could not allocate a chain of nclsts clusters */
  809.             fat_node_put(nodep);
  810.             ipc_answer_0(callid, status);
  811.             ipc_answer_0(rid, status);
  812.             return;
  813.         }
  814.         /* zero fill any gaps */
  815.         fat_fill_gap(bs, nodep, mcl, pos);
  816.         b = _fat_block_get(bs, dev_handle, lcl, (pos / bps) % spc,
  817.             flags);
  818.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  819.             bytes);
  820.         b->dirty = true;        /* need to sync block */
  821.         block_put(b);
  822.         /*
  823.          * Append the cluster chain starting in mcl to the end of the
  824.          * node's cluster chain.
  825.          */
  826.         fat_append_clusters(bs, nodep, mcl);
  827.         nodep->size = pos + bytes;
  828.         nodep->dirty = true;        /* need to sync node */
  829.         ipc_answer_2(rid, EOK, bytes, nodep->size);
  830.         fat_node_put(nodep);
  831.         return;
  832.     }
  833. }
  834.  
  835. void fat_truncate(ipc_callid_t rid, ipc_call_t *request)
  836. {
  837.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  838.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  839.     size_t size = (off_t)IPC_GET_ARG3(*request);
  840.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  841.     fat_bs_t *bs;
  842.     uint16_t bps;
  843.     uint8_t spc;
  844.     unsigned bpc;   /* bytes per cluster */
  845.     int rc;
  846.  
  847.     if (!nodep) {
  848.         ipc_answer_0(rid, ENOENT);
  849.         return;
  850.     }
  851.  
  852.     bs = block_bb_get(dev_handle);
  853.     bps = uint16_t_le2host(bs->bps);
  854.     spc = bs->spc;
  855.     bpc = bps * spc;
  856.  
  857.     if (nodep->size == size) {
  858.         rc = EOK;
  859.     } else if (nodep->size < size) {
  860.         /*
  861.          * The standard says we have the freedom to grow the node.
  862.          * For now, we simply return an error.
  863.          */
  864.         rc = EINVAL;
  865.     } else if (ROUND_UP(nodep->size, bpc) == ROUND_UP(size, bpc)) {
  866.         /*
  867.          * The node will be shrunk, but no clusters will be deallocated.
  868.          */
  869.         nodep->size = size;
  870.         nodep->dirty = true;        /* need to sync node */
  871.         rc = EOK;  
  872.     } else {
  873.         /*
  874.          * The node will be shrunk, clusters will be deallocated.
  875.          */
  876.         if (size == 0) {
  877.             fat_chop_clusters(bs, nodep, FAT_CLST_RES0);
  878.         } else {
  879.             fat_cluster_t lastc;
  880.             (void) fat_cluster_walk(bs, dev_handle, nodep->firstc,
  881.                 &lastc, (size - 1) / bpc);
  882.             fat_chop_clusters(bs, nodep, lastc);
  883.         }
  884.         nodep->size = size;
  885.         nodep->dirty = true;        /* need to sync node */
  886.         rc = EOK;  
  887.     }
  888.     fat_node_put(nodep);
  889.     ipc_answer_0(rid, rc);
  890.     return;
  891. }
  892.  
  893. void fat_destroy(ipc_callid_t rid, ipc_call_t *request)
  894. {
  895.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  896.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  897.     int rc;
  898.  
  899.     fat_node_t *nodep = fat_node_get(dev_handle, index);
  900.     if (!nodep) {
  901.         ipc_answer_0(rid, ENOENT);
  902.         return;
  903.     }
  904.  
  905.     rc = fat_destroy_node(nodep);
  906.     ipc_answer_0(rid, rc);
  907. }
  908.  
  909. /**
  910.  * @}
  911.  */
  912.