spritehttpd/lib/espfs/espfs.c

/*
This is a simple read-only implementation of a file system. It uses a block of data coming from the
mkespfsimg tool, and can use that block to do abstracted operations on the files that are in there.
It's written for use with httpd, but doesn't need to be used as such.
*/

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * Jeroen Domburg <jeroen@spritesmods.com> wrote this file. As long as you retain
 * this notice you can do whatever you want with this stuff. If we meet some day,
 * and you think this stuff is worth it, you can buy me a beer in return.
 * ----------------------------------------------------------------------------
 */


#include <stdio.h>
#include <stdint.h>
#include <string.h>

#include "espfsformat.h"
#include "espfs.h"

#include "heatshrink_decoder.h"
#include "logging.h"

// forward declaration for use in the stand-alone espfs tool
int httpdPlatEspfsRead(void *dest, uint32_t offset, size_t len);

struct EspFsFile {
  uint32_t header;
  char decompressor;
  uint32_t posDecomp;
  uint32_t posStart;
  uint32_t posComp;
  heatshrink_decoder *decompData;
};


EspFsInitResult espFsInit()
{
    // check if there is valid header at address
    EspFsHeader testHeader;
    int rv;
    rv = httpdPlatEspfsRead(&testHeader, 0, sizeof(EspFsHeader));
    if (rv != 0 || testHeader.magic != ESPFS_MAGIC) {
        espfs_error("[EspFS] Invalid magic on first file header");
        return ESPFS_INIT_RESULT_NO_IMAGE;
    }
    return ESPFS_INIT_RESULT_OK;
}

// Returns flags of opened file.
int espFsFlags(EspFsFile *fh)
{
    if (fh == NULL) {
        espfs_error("[EspFS] File handle not ready");
        return -1;
    }

    int8_t flags;
    httpdPlatEspfsRead(&flags, fh->header + offsetof(EspFsHeader, flags), 1);
    return (int) flags;
}

void espFsWalkInit(EspFsWalk *walk)
{
    if (!walk) { return; }
    walk->hpos = 0;
}

bool espFsWalkNext(EspFsWalk *walk, EspFsHeader *header, char *namebuf, size_t namebuf_cap, uint32_t *filepos)
{
    int rv;

    if (!header || !namebuf) {
        espfs_error("[EspFS] espFsWalkNext NULL header or namebuf arg");
        return false;
    }

    uint32_t p = walk->hpos;

    //Grab the next file header.
    rv = httpdPlatEspfsRead(header, p, sizeof(EspFsHeader));
    if (rv != 0) {
        return false;
    }

    if (header->magic != ESPFS_MAGIC) {
        espfs_error("[EspFS] Magic mismatch. EspFS image broken.");
        return false;
    }

    if (header->flags & FLAG_LASTFILE) {
        espfs_dbg("[EspFS] End of image.");
        return false;
    }

    if (header->nameLen > namebuf_cap) {
        espfs_dbg("[EspFS] Name too long for buffer");
        return false;
    }

    //Grab the name of the file.
    p += sizeof(EspFsHeader);
    httpdPlatEspfsRead(namebuf, p, header->nameLen);
    namebuf[header->nameLen] = 0; // ensure it's terminated

    if (filepos) {
        *filepos = walk->hpos;
    }

    walk->hpos += sizeof(EspFsHeader) + header->nameLen + header->fileLenComp;
    // Align
    while(walk->hpos & 3) {
        walk->hpos++;
    }

    return true;
}

//Open a file and return a pointer to the file desc struct.
EspFsFile *espFsOpenFromHeader(EspFsHeader *h, uint32_t hpos)
{
    int rv;
    if (h->magic != ESPFS_MAGIC) {
        espfs_error("[EspFS] Magic mismatch. EspFS image broken.");
        return NULL;
    }
    if (h->flags & FLAG_LASTFILE) {
        espfs_dbg("[EspFS] End of image.");
        return NULL;
    }

    hpos += sizeof(EspFsHeader);
    hpos += h->nameLen; // Skip to content

    EspFsFile *r = (EspFsFile *) httpdPlatMalloc(sizeof(EspFsFile)); //Alloc file desc mem
    if (r == NULL) { return NULL; }
    r->header = hpos;
    r->decompressor = h->compression;
    r->posComp = hpos;
    r->posStart = hpos;
    r->posDecomp = 0;

    espfs_dbg("[EspFS] Found file @ hpos %d", hpos);

    if (h->compression == COMPRESS_NONE) {
        r->decompData = NULL;
    } else if (h->compression == COMPRESS_HEATSHRINK) {
        //File is compressed with Heatshrink.
        char parm;
        //Decoder params are stored in 1st byte.
        rv = httpdPlatEspfsRead(&parm, r->posComp, 1);
        if (rv != 0) {
            return NULL;
        }
        r->posComp++;
        espfs_dbg("[EspFS] Heatshrink compressed file; decode parms = %x", parm);
        heatshrink_decoder *dec = heatshrink_decoder_alloc(16, (parm >> 4) & 0xf, parm & 0xf);
        r->decompData = dec;
        return r;
    } else {
        espfs_error("[EspFS] Invalid compression: %d", h->compression);
        httpdPlatFree(r);
        return NULL;
    }
}

//Open a file and return a pointer to the file desc struct.
EspFsFile *espFsOpenAt(uint32_t hpos)
{
    EspFsHeader h;
    int rv = httpdPlatEspfsRead(&h, hpos, sizeof(EspFsHeader));
    if (rv != 0) {
        return NULL;
    }
    return espFsOpenFromHeader(&h, hpos);
}


//Open a file and return a pointer to the file desc struct.
EspFsFile *espFsOpen(const char *fileName)
{
    int rv;
    uint32_t p = 0;
    uint32_t hpos;
    char namebuf[256];
    EspFsHeader h;
    EspFsFile *r;
    //Strip initial slashes
    while (fileName[0] == '/') { fileName++; }

    espfs_dbg("[EspFS] Open file: %s", fileName);

    //Go find that file!
    while (1) {
        hpos = p;
        //Grab the next file header.
        rv = httpdPlatEspfsRead(&h, p, sizeof(EspFsHeader));
        if (rv != 0) {
            return NULL;
        }

        if (h.magic != ESPFS_MAGIC) {
            espfs_error("[EspFS] Magic mismatch. EspFS image broken.");
            return NULL;
        }
        if (h.flags & FLAG_LASTFILE) {
            espfs_dbg("[EspFS] End of image.");
            return NULL;
        }

        //Grab the name of the file.
        p += sizeof(EspFsHeader);
        rv = httpdPlatEspfsRead(&namebuf, p, h.nameLen);
        if (rv != 0) {
            return NULL;
        }
        namebuf[h.nameLen] = 0; // ensure it's terminated

        if (strcmp(namebuf, fileName) == 0) {
            //Yay, this is the file we need!
            return espFsOpenFromHeader(&h, hpos);
        }
        //We don't need this file. Skip name and file
        p += h.nameLen + h.fileLenComp;
        while(p & 3) {
            p++;
        }
    }
}

//Read len bytes from the given file into buff. Returns the actual amount of bytes read.
int espFsRead(EspFsFile *fh, char *buff, size_t len)
{
    int rv;
    int flen;
    int fdlen;
    if (fh == NULL) { return 0; }

    rv = httpdPlatEspfsRead(&flen, fh->header + offsetof(EspFsHeader, fileLenComp), 4);
    if (rv != 0) {
        return 0;
    }

    //Cache file length.
    //Do stuff depending on the way the file is compressed.
    if (fh->decompressor == COMPRESS_NONE) {
        int toRead = flen - (int) (fh->posComp - fh->posStart);
        if (toRead < 0) { toRead = 0; }
        if (len > toRead) { len = toRead; }
        rv = httpdPlatEspfsRead(buff, fh->posComp, len);
        if (rv != 0) {
            return 0;
        }

        fh->posDecomp += len;
        fh->posComp += len;
        return (int) len;
    } else if (fh->decompressor == COMPRESS_HEATSHRINK) {
        rv = httpdPlatEspfsRead(&fdlen, fh->header + offsetof(EspFsHeader, fileLenDecomp), 4);
        if (rv != 0) {
            return 0;
        }

        size_t decoded = 0;
        size_t elen, rlen;
        char ebuff[16];
        heatshrink_decoder *dec = fh->decompData;
        if (fh->posDecomp == fdlen) {
            return 0;
        }

        // We must ensure that whole file is decompressed and written to output buffer.
        // This means even when there is no input data (elen==0) try to poll decoder until
        // posDecomp equals decompressed file length

        while (decoded < len) {
            //Feed data into the decompressor
            //ToDo: Check ret val of heatshrink fns for errors
            elen = flen - (fh->posComp - fh->posStart);
            if (elen > 0) {
                rv = httpdPlatEspfsRead(ebuff, fh->posComp, 16);
                if (rv != 0) {
                    return 0;
                }

                heatshrink_decoder_sink(dec, (uint8_t *) ebuff, (elen > 16) ? 16 : elen, &rlen);
                fh->posComp += rlen;
            }
            //Grab decompressed data and put into buff
            heatshrink_decoder_poll(dec, (uint8_t *) buff, len - decoded, &rlen);
            fh->posDecomp += rlen;
            buff += rlen;
            decoded += rlen;

            if (elen == 0) {
                if (fh->posDecomp == fdlen) {
                    heatshrink_decoder_finish(dec);
                }
                return (int) decoded;
            }
        }
        return (int) len;
    }
    return 0;
}

//Close the file.
void espFsClose(EspFsFile *fh)
{
    if (fh == NULL) { return; }
    if (fh->decompressor == COMPRESS_HEATSHRINK) {
        heatshrink_decoder *dec = (heatshrink_decoder *) fh->decompData;
        heatshrink_decoder_free(dec);
    }
    httpdPlatFree(fh);
}