From 917892ea7d676c0937f1921bb126b200b2dea329 Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Thu, 2 Aug 2018 15:47:49 -0500
Subject: Move pending/compress.c to lib/deflate.c, first pass at genericizing
 it.

---
 lib/deflate.c | 485 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 485 insertions(+)
 create mode 100644 lib/deflate.c

(limited to 'lib')

diff --git a/lib/deflate.c b/lib/deflate.c
new file mode 100644
index 00000000..2a6274e7
--- /dev/null
+++ b/lib/deflate.c
@@ -0,0 +1,485 @@
+/* deflate.c - deflate/inflate code for gzip and friends
+ *
+ * Copyright 2014 Rob Landley <rob@landley.net>
+ *
+ * See RFCs 1950 (zlib), 1951 (deflate), and 1952 (gzip)
+ * LSB 4.1 has gzip, gunzip, and zcat
+ *
+ * TODO: zip -d DIR -x LIST -list -quiet -no overwrite -overwrite -p to stdout
+ */
+
+#include "toys.h"
+
+struct deflate {
+  // Huffman codes: base offset and extra bits tables (length and distance)
+  char lenbits[29], distbits[30];
+  unsigned short lenbase[29], distbase[30];
+  void *fixdisthuff, *fixlithuff;
+
+  // CRC
+  void (*crcfunc)(struct deflate *dd, char *data, int len);
+  unsigned crctable[256], crc;
+
+
+  // Tables only used for deflation
+  unsigned short *hashhead, *hashchain;
+
+  // Compressed data buffer (extra space malloced at end)
+  unsigned pos, len;
+  int infd, outfd;
+  char data[];
+};
+
+// little endian bit buffer
+struct bitbuf {
+  int fd, bitpos, len, max;
+  char buf[];
+};
+
+// malloc a struct bitbuf
+struct bitbuf *bitbuf_init(int fd, int size)
+{
+  struct bitbuf *bb = xzalloc(sizeof(struct bitbuf)+size);
+
+  bb->max = size;
+  bb->fd = fd;
+
+  return bb;
+}
+
+// Advance bitpos without the overhead of recording bits
+// Loads more data when input buffer empty
+void bitbuf_skip(struct bitbuf *bb, int bits)
+{
+  int pos = bb->bitpos + bits, len = bb->len << 3;
+
+  while (pos >= len) {
+    pos -= len;
+    len = (bb->len = read(bb->fd, bb->buf, bb->max)) << 3;
+    if (bb->len < 1) perror_exit("inflate EOF");
+  }
+  bb->bitpos = pos;
+}
+
+// Optimized single bit inlined version
+static inline int bitbuf_bit(struct bitbuf *bb)
+{
+  int bufpos = bb->bitpos>>3;
+
+  if (bufpos == bb->len) {
+    bitbuf_skip(bb, 0);
+    bufpos = 0;
+  }
+
+  return (bb->buf[bufpos]>>(bb->bitpos++&7))&1;
+}
+
+// Fetch the next X bits from the bitbuf, little endian
+unsigned bitbuf_get(struct bitbuf *bb, int bits)
+{
+  int result = 0, offset = 0;
+
+  while (bits) {
+    int click = bb->bitpos >> 3, blow, blen;
+
+    // Load more data if buffer empty
+    if (click == bb->len) bitbuf_skip(bb, click = 0);
+
+    // grab bits from next byte
+    blow = bb->bitpos & 7;
+    blen = 8-blow;
+    if (blen > bits) blen = bits;
+    result |= ((bb->buf[click] >> blow) & ((1<<blen)-1)) << offset;
+    offset += blen;
+    bits -= blen;
+    bb->bitpos += blen;
+  }
+
+  return result;
+}
+
+void bitbuf_flush(struct bitbuf *bb)
+{
+  if (!bb->bitpos) return;
+
+  xwrite(bb->fd, bb->buf, (bb->bitpos+7)>>3);
+  memset(bb->buf, 0, bb->max);
+  bb->bitpos = 0;
+}
+
+void bitbuf_put(struct bitbuf *bb, int data, int len)
+{
+  while (len) {
+    int click = bb->bitpos >> 3, blow, blen;
+
+    // Flush buffer if necessary
+    if (click == bb->max) {
+      bitbuf_flush(bb);
+      click = 0;
+    }
+    blow = bb->bitpos & 7;
+    blen = 8-blow;
+    if (blen > len) blen = len;
+    bb->buf[click] |= data << blow;
+    bb->bitpos += blen;
+    data >>= blen;
+    len -= blen;
+  }
+}
+
+static void output_byte(struct deflate *dd, char sym)
+{
+  int pos = dd->pos++ & 32767;
+
+  dd->data[pos] = sym;
+
+  if (pos == 32767) {
+    xwrite(dd->outfd, dd->data, 32768);
+    if (dd->crcfunc) dd->crcfunc(dd, dd->data, 32768);
+  }
+}
+
+// Huffman coding uses bits to traverse a binary tree to a leaf node,
+// By placing frequently occurring symbols at shorter paths, frequently
+// used symbols may be represented in fewer bits than uncommon symbols.
+// (length[0] isn't used but code's clearer if it's there.)
+
+struct huff {
+  unsigned short length[16];  // How many symbols have this bit length?
+  unsigned short symbol[288]; // sorted by bit length, then ascending order
+};
+
+// Create simple huffman tree from array of bit lengths.
+
+// The symbols in the huffman trees are sorted (first by bit length
+// of the code to reach them, then by symbol number). This means that given
+// the bit length of each symbol, we can construct a unique tree.
+static void len2huff(struct huff *huff, char bitlen[], int len)
+{
+  int offset[16];
+  int i;
+
+  // Count number of codes at each bit length
+  memset(huff, 0, sizeof(struct huff));
+  for (i = 0; i<len; i++) huff->length[bitlen[i]]++;
+
+  // Sort symbols by bit length, then symbol. Get list of starting positions
+  // for each group, then write each symbol to next position within its group.
+  *huff->length = *offset = 0;
+  for (i = 1; i<16; i++) offset[i] = offset[i-1] + huff->length[i-1];
+  for (i = 0; i<len; i++) if (bitlen[i]) huff->symbol[offset[bitlen[i]]++] = i;
+}
+
+// Fetch and decode next huffman coded symbol from bitbuf.
+// This takes advantage of the sorting to navigate the tree as an array:
+// each time we fetch a bit we have all the codes at that bit level in
+// order with no gaps.
+static unsigned huff_and_puff(struct bitbuf *bb, struct huff *huff)
+{
+  unsigned short *length = huff->length;
+  int start = 0, offset = 0;
+
+  // Traverse through the bit lengths until our code is in this range
+  for (;;) {
+    offset = (offset << 1) | bitbuf_bit(bb);
+    start += *++length;
+    if ((offset -= *length) < 0) break;
+    if ((length - huff->length) & 16) error_exit("bad symbol");
+  }
+
+  return huff->symbol[start + offset];
+}
+
+// Decompress deflated data from bitbuf to dd->outfd.
+static void inflate(struct deflate *dd, struct bitbuf *bb)
+{
+  dd->crc = ~0;
+  // repeat until spanked
+  for (;;) {
+    int final, type;
+
+    final = bitbuf_get(bb, 1);
+    type = bitbuf_get(bb, 2);
+
+    if (type == 3) error_exit("bad type");
+
+    // Uncompressed block?
+    if (!type) {
+      int len, nlen;
+
+      // Align to byte, read length
+      bitbuf_skip(bb, (8-bb->bitpos)&7);
+      len = bitbuf_get(bb, 16);
+      nlen = bitbuf_get(bb, 16);
+      if (len != (0xffff & ~nlen)) error_exit("bad len");
+
+      // Dump literal output data
+      while (len) {
+        int pos = bb->bitpos >> 3, bblen = bb->len - pos;
+        char *p = bb->buf+pos;
+
+        // dump bytes until done or end of current bitbuf contents
+        if (bblen > len) bblen = len;
+        pos = bblen;
+        while (pos--) output_byte(dd, *(p++));
+        bitbuf_skip(bb, bblen << 3);
+        len -= bblen;
+      }
+
+    // Compressed block
+    } else {
+      struct huff *disthuff, *lithuff;
+
+      // Dynamic huffman codes?
+      if (type == 2) {
+        struct huff *h2 = ((struct huff *)toybuf)+1;
+        int i, litlen, distlen, hufflen;
+        char *hufflen_order = "\x10\x11\x12\0\x08\x07\x09\x06\x0a\x05\x0b"
+                              "\x04\x0c\x03\x0d\x02\x0e\x01\x0f", *bits;
+
+        // The huffman trees are stored as a series of bit lengths
+        litlen = bitbuf_get(bb, 5)+257;  // max 288
+        distlen = bitbuf_get(bb, 5)+1;   // max 32
+        hufflen = bitbuf_get(bb, 4)+4;   // max 19
+
+        // The literal and distance codes are themselves compressed, in
+        // a complicated way: an array of bit lengths (hufflen many
+        // entries, each 3 bits) is used to fill out an array of 19 entries
+        // in a magic order, leaving the rest 0. Then make a tree out of it:
+        memset(bits = toybuf+1, 0, 19);
+        for (i=0; i<hufflen; i++) bits[hufflen_order[i]] = bitbuf_get(bb, 3);
+        len2huff(h2, bits, 19);
+
+        // Use that tree to read in the literal and distance bit lengths
+        for (i = 0; i < litlen + distlen;) {
+          int sym = huff_and_puff(bb, h2);
+
+          // 0-15 are literals, 16 = repeat previous code 3-6 times,
+          // 17 = 3-10 zeroes (3 bit), 18 = 11-138 zeroes (7 bit)
+          if (sym < 16) bits[i++] = sym;
+          else {
+            int len = sym & 2;
+
+            len = bitbuf_get(bb, sym-14+len+(len>>1)) + 3 + (len<<2);
+            memset(bits+i, bits[i-1] * !(sym&3), len);
+            i += len;
+          }
+        }
+        if (i > litlen+distlen) error_exit("bad tree");
+
+        len2huff(lithuff = h2, bits, litlen);
+        len2huff(disthuff = ((struct huff *)toybuf)+2, bits+litlen, distlen);
+
+      // Static huffman codes
+      } else {
+        lithuff = dd->fixlithuff;
+        disthuff = dd->fixdisthuff;
+      }
+
+      // Use huffman tables to decode block of compressed symbols
+      for (;;) {
+        int sym = huff_and_puff(bb, lithuff);
+
+        // Literal?
+        if (sym < 256) output_byte(dd, sym);
+
+        // Copy range?
+        else if (sym > 256) {
+          int len, dist;
+
+          sym -= 257;
+          len = dd->lenbase[sym] + bitbuf_get(bb, dd->lenbits[sym]);
+          sym = huff_and_puff(bb, disthuff);
+          dist = dd->distbase[sym] + bitbuf_get(bb, dd->distbits[sym]);
+          sym = dd->pos & 32767;
+
+          while (len--) output_byte(dd, dd->data[(dd->pos-dist) & 32767]);
+
+        // End of block
+        } else break;
+      }
+    }
+
+    // Was that the last block?
+    if (final) break;
+  }
+
+  if (dd->pos & 32767) {
+    xwrite(dd->outfd, dd->data, dd->pos&32767);
+    if (dd->crcfunc) dd->crcfunc(dd, dd->data, dd->pos&32767);
+  }
+}
+
+// Deflate from dd->infd to bitbuf
+// For deflate, dd->len = input read, dd->pos = input consumed
+static void deflate(struct deflate *dd, struct bitbuf *bb)
+{
+  char *data = dd->data;
+  int len, final = 0;
+
+  dd->crc = ~0;
+
+  while (!final) {
+    // Read next half-window of data if we haven't hit EOF yet.
+    len = readall(dd->infd, data+(dd->len&32768), 32768);
+    if (len < 0) perror_exit("read"); // todo: add filename
+    if (len != 32768) final++;
+    if (dd->crcfunc) dd->crcfunc(dd, data+(dd->len&32768), len);
+    // dd->len += len;  crcfunc advances len TODO
+
+    // store block as literal
+    bitbuf_put(bb, final, 1);
+    bitbuf_put(bb, 0, 1);
+
+    bitbuf_put(bb, 0, (8-bb->bitpos)&7);
+    bitbuf_put(bb, len, 16);
+    bitbuf_put(bb, 0xffff & ~len, 16);
+
+    // repeat until spanked
+    while (dd->pos != dd->len) {
+      unsigned pos = dd->pos&65535;
+
+      bitbuf_put(bb, data[pos], 8);
+
+      // need to refill buffer?
+      if (!(32767 & ++dd->pos) && !final) break;
+    }
+  }
+  bitbuf_flush(bb);
+}
+
+// Allocate memory for deflate/inflate.
+static struct deflate *init_deflate(int compress)
+{
+  int i, n = 1;
+  struct deflate *dd = xmalloc(sizeof(struct deflate)+32768*(compress ? 4 : 1));
+
+// TODO sizeof and order of these?
+  // decompress needs 32k history, compress adds 64k hashhead and 32k hashchain
+  if (compress) {
+    dd->hashhead = (unsigned short *)(dd->data+65536);
+    dd->hashchain = (unsigned short *)(dd->data+65536+32768);
+  }
+
+  // Calculate lenbits, lenbase, distbits, distbase
+  *dd->lenbase = 3;
+  for (i = 0; i<sizeof(dd->lenbits)-1; i++) {
+    if (i>4) {
+      if (!(i&3)) {
+        dd->lenbits[i]++;
+        n <<= 1;
+      }
+      if (i == 27) n--;
+      else dd->lenbits[i+1] = dd->lenbits[i];
+    }
+    dd->lenbase[i+1] = n + dd->lenbase[i];
+  }
+  n = 0;
+  for (i = 0; i<sizeof(dd->distbits); i++) {
+    dd->distbase[i] = 1<<n;
+    if (i) dd->distbase[i] += dd->distbase[i-1];
+    if (i>3 && !(i&1)) n++;
+    dd->distbits[i] = n;
+  }
+
+// TODO layout and lifetime of this?
+  // Init fixed huffman tables
+  for (i=0; i<288; i++) toybuf[i] = 8 + (i>143) - ((i>255)<<1) + (i>279);
+  len2huff(dd->fixlithuff = ((struct huff *)toybuf)+3, toybuf, 288);
+  memset(toybuf, 5, 30);
+  len2huff(dd->fixdisthuff = ((struct huff *)toybuf)+4, toybuf, 30);
+
+  return dd;
+}
+
+// Return true/false whether we consumed a gzip header.
+static int is_gzip(struct bitbuf *bb)
+{
+  int flags;
+
+  // Confirm signature
+  if (bitbuf_get(bb, 24) != 0x088b1f || (flags = bitbuf_get(bb, 8)) > 31)
+    return 0;
+  bitbuf_skip(bb, 6*8);
+
+  // Skip extra, name, comment, header CRC fields
+  if (flags & 4) bitbuf_skip(bb, 16);
+  if (flags & 8) while (bitbuf_get(bb, 8));
+  if (flags & 16) while (bitbuf_get(bb, 8));
+  if (flags & 2) bitbuf_skip(bb, 16);
+
+  return 1;
+}
+
+void gzip_crc(struct deflate *dd, char *data, int len)
+{
+  int i;
+  unsigned crc, *crc_table = dd->crctable;
+
+  crc = dd->crc;
+  for (i=0; i<len; i++) crc = crc_table[(crc^data[i])&0xff] ^ (crc>>8);
+  dd->crc = crc;
+  dd->len += len;
+}
+
+long long gzip_fd(int infd, int outfd)
+{
+  struct bitbuf *bb = bitbuf_init(outfd, 4096);
+  struct deflate *dd = init_deflate(1);
+  long long rc;
+
+  // Header from RFC 1952 section 2.2:
+  // 2 ID bytes (1F, 8b), gzip method byte (8=deflate), FLAG byte (none),
+  // 4 byte MTIME (zeroed), Extra Flags (2=maximum compression),
+  // Operating System (FF=unknown)
+ 
+  dd->infd = infd;
+  xwrite(bb->fd, "\x1f\x8b\x08\0\0\0\0\0\x02\xff", 10);
+
+  // Little endian crc table
+  crc_init(dd->crctable, 1);
+  dd->crcfunc = gzip_crc;
+
+  deflate(dd, bb);
+
+  // tail: crc32, len32
+
+  bitbuf_put(bb, 0, (8-bb->bitpos)&7);
+  bitbuf_put(bb, ~dd->crc, 32);
+  bitbuf_put(bb, dd->len, 32);
+  rc = dd->len;
+
+  bitbuf_flush(bb);
+  free(bb);
+  free(dd);
+
+  return rc;
+}
+
+long long gunzip_fd(int infd, int outfd)
+{
+  struct bitbuf *bb = bitbuf_init(infd, 4096);
+  struct deflate *dd = init_deflate(0);
+  long long rc;
+
+  if (!is_gzip(bb)) error_exit("not gzip");
+  dd->outfd = outfd;
+
+  // Little endian crc table
+  crc_init(dd->crctable, 1);
+  dd->crcfunc = gzip_crc;
+
+  inflate(dd, bb);
+
+  // tail: crc32, len32
+
+  bitbuf_skip(bb, (8-bb->bitpos)&7);
+  if (~dd->crc != bitbuf_get(bb, 32) || dd->len != bitbuf_get(bb, 32))
+    error_exit("bad crc");
+
+  rc = dd->len;
+  free(bb);
+  free(dd);
+
+  return rc;
+}
-- 
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