Remove CRC16 from dumped mruby binary.

`calc_crc_16_ccitt()` consumes a lot of clock cycles in programs like
`mrbtest` which loads a lot of dumped binary. Error detection for flaky
channels should be done in the higher level.

Note: `mruby/c` should be updated to support this change.

3 files changed, 3 insertions, 65 deletions

diff --git a/src/crc.c b/src/crc.c
deleted file mode 100644
index 290b2ca0e..000000000
--- a/src/crc.c
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
-** crc.c - calculate CRC
-**
-** See Copyright Notice in mruby.h
-*/
-
-#include <limits.h>
-#include <stdint.h>
-#include <stddef.h>
-
-/* Calculate CRC (CRC-16-CCITT)
-**
-**  0000_0000_0000_0000_0000_0000_0000_0000
-**          ^|------- CRC -------|- work --|
-**        carry
-*/
-#define  CRC_16_CCITT       0x11021ul        /* x^16+x^12+x^5+1 */
-#define  CRC_XOR_PATTERN    (CRC_16_CCITT << 8)
-#define  CRC_CARRY_BIT      (0x01000000)
-
-uint16_t
-calc_crc_16_ccitt(const uint8_t *src, size_t nbytes, uint16_t crc)
-{
-  size_t ibyte;
-  uint32_t ibit;
-  uint32_t crcwk = crc << 8;
-
-  for (ibyte = 0; ibyte < nbytes; ibyte++) {
-    crcwk |= *src++;
-    for (ibit = 0; ibit < CHAR_BIT; ibit++) {
-      crcwk <<= 1;
-      if (crcwk & CRC_CARRY_BIT) {
-        crcwk ^= CRC_XOR_PATTERN;
-      }
-    }
-  }
-  return (uint16_t)(crcwk >> 8);
-}
-
diff --git a/src/dump.c b/src/dump.c
index 79908b47f..10b6d9dec 100644
--- a/src/dump.c
+++ b/src/dump.c
@@ -747,8 +747,6 @@ static int
 write_rite_binary_header(mrb_state *mrb, size_t binary_size, uint8_t *bin, uint8_t flags)
 {
   struct rite_binary_header *header = (struct rite_binary_header *)bin;
-  uint16_t crc;
-  uint32_t offset;
 
   memcpy(header->binary_ident, RITE_BINARY_IDENT, sizeof(header->binary_ident));
   memcpy(header->major_version, RITE_BINARY_MAJOR_VER, sizeof(header->major_version));
@@ -758,10 +756,6 @@ write_rite_binary_header(mrb_state *mrb, size_t binary_size, uint8_t *bin, uint8
   mrb_assert(binary_size <= UINT32_MAX);
   uint32_to_bin((uint32_t)binary_size, header->binary_size);
 
-  offset = (uint32_t)((&(header->binary_crc[0]) - bin) + sizeof(uint16_t));
-  crc = calc_crc_16_ccitt(bin + offset, binary_size - offset, 0);
-  uint16_to_bin(crc, header->binary_crc);
-
   return MRB_DUMP_OK;
 }
 
diff --git a/src/load.c b/src/load.c
index 0b98fba66..cf8454f1c 100644
--- a/src/load.c
+++ b/src/load.c
@@ -37,13 +37,6 @@
     return irep; \
   }
 
-static size_t
-offset_crc_body(void)
-{
-  struct rite_binary_header header;
-  return ((uint8_t *)header.binary_crc - (uint8_t *)&header) + sizeof(header.binary_crc);
-}
-
 #ifndef MRB_NO_FLOAT
 static double
 str_to_double(mrb_state *mrb, const char *p)
@@ -519,7 +512,7 @@ lv_exit:
 }
 
 static int
-read_binary_header(const uint8_t *bin, size_t bufsize, size_t *bin_size, uint16_t *crc, uint8_t *flags)
+read_binary_header(const uint8_t *bin, size_t bufsize, size_t *bin_size, uint8_t *flags)
 {
   const struct rite_binary_header *header = (const struct rite_binary_header *)bin;
 
@@ -540,9 +533,6 @@ read_binary_header(const uint8_t *bin, size_t bufsize, size_t *bin_size, uint16_
     return MRB_DUMP_INVALID_FILE_HEADER;
   }
 
-  if (crc) {
-    *crc = bin_to_uint16(header->binary_crc);
-  }
   *bin_size = (size_t)bin_to_uint32(header->binary_size);
 
   if (bufsize < *bin_size) {
@@ -559,24 +549,17 @@ read_irep(mrb_state *mrb, const uint8_t *bin, size_t bufsize, uint8_t flags)
   struct RProc *proc = NULL;
   mrb_irep *irep = NULL;
   const struct rite_section_header *section_header;
-  uint16_t crc;
   size_t bin_size = 0;
-  size_t n;
 
   if ((mrb == NULL) || (bin == NULL)) {
     return NULL;
   }
 
-  result = read_binary_header(bin, bufsize, &bin_size, &crc, &flags);
+  result = read_binary_header(bin, bufsize, &bin_size, &flags);
   if (result != MRB_DUMP_OK) {
     return NULL;
   }
 
-  n = offset_crc_body();
-  if (crc != calc_crc_16_ccitt(bin + n, bin_size - n, 0)) {
-    return NULL;
-  }
-
   bin += sizeof(struct rite_binary_header);
   do {
     section_header = (const struct rite_section_header *)bin;
@@ -705,7 +688,7 @@ mrb_proc_read_irep_file(mrb_state *mrb, FILE *fp)
   if (fread(buf, header_size, 1, fp) == 0) {
     goto irep_exit;
   }
-  result = read_binary_header(buf, (size_t)-1, &buf_size, NULL, &flags);
+  result = read_binary_header(buf, (size_t)-1, &buf_size, &flags);
   if (result != MRB_DUMP_OK || buf_size <= header_size) {
     goto irep_exit;
   }