number of bytes skipped by SKIPDATA option depends on arch

cs.c

@@ -294,6 +294,7 @@ static void fill_insn(struct cs_struct *handle, cs_insn *insn, char *buffer, MCI
 }
 
 // how many bytes will we skip when encountering data (CS_OPT_SKIPDATA)?
+// this very much depends on instruction alignment requirement of each arch.
 static uint8_t skipdata_size(cs_struct *handle)
 {
 	switch(handle->arch) {
@@ -301,12 +302,20 @@ static uint8_t skipdata_size(cs_struct *handle)
 			// should never reach
 			return -1;
 		case CS_ARCH_ARM:
+			// skip 2 bytes on Thumb mode.
+			if (handle->mode & CS_MODE_THUMB)
+				return 2;
+			// otherwise, skip 4 bytes
+			return 4;
 		case CS_ARCH_ARM64:
 		case CS_ARCH_MIPS:
 		case CS_ARCH_PPC:
 		case CS_ARCH_SPARC:
+			// skip 4 bytes
+			return 4;
 		case CS_ARCH_SYSZ:
-			// skip 2 bytes due to instruction alignment
+			// SystemZ instruction's length can be 2, 4 or 6 bytes,
+			// so we just skip 2 bytes
 			return 2;
 		case CS_ARCH_X86:
 			// X86 has no restriction on instruction alignment

include/capstone.h

@@ -118,13 +118,22 @@ typedef struct cs_opt_skipdata {
 	// User can specify the string for this instruction's "mnemonic" here.
 	// By default (if @mnemonic is NULL), Capstone use ".db".
 	const char *mnemonic;
+
 	// User-defined callback function to be called when Capstone hits data.
-	// If the returned value from this callback is positive (>0), Capstone will skip exactly
-	// that number of bytes & continue. Otherwise, if the callback returns 0, Capstone stops
-	// disassembling and returns immediately from cs_disasm_ex()
-	// NOTE: if this callback pointer is NULL, Capstone skip 1 byte on X86, and 2 bytes on
-	// every other architectures.
+	// If the returned value from this callback is positive (>0), Capstone
+	// will skip exactly that number of bytes & continue. Otherwise, if
+	// the callback returns 0, Capstone stops disassembling and returns
+	// immediately from cs_disasm_ex()
+	// NOTE: if this callback pointer is NULL, Capstone would skip a number
+	// of bytes depending on architectures, as following:
+	// Arm:     2 bytes (Thumb mode) or 4 bytes.
+	// Arm64:   4 bytes.
+	// Mips:    4 bytes.
+	// Sparc:   4 bytes.
+	// SystemZ: 2 bytes.
+	// X86:     1 bytes.
 	cs_skipdata_cb_t callback; 	// default value is NULL
+
 	// User-defined data to be passed to @callback function pointer.
 	void *user_data;
 } cs_opt_skipdata;