Add READ_FLASH_UINT8, allowing ESP8266 to read&exec strings stored in…

… Flash with E.memoryArea
espruino · Jan 26, 2016 · cadc44c · cadc44c
1 parent 391ae89
commit cadc44c
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Showing 5 changed files with 30 additions and 24 deletions.
diff --git a/ChangeLog b/ChangeLog
@@ -26,6 +26,7 @@
             Only garbage collect on idle if we're low on memory (fix #767)
             Improve malloc behaviour for crypto lib (try and free all command history is first alloc fails)
             Improve HTTPS error messages
+            Add READ_FLASH_UINT8, allowing ESP8266 to read&exec strings stored in Flash with E.memoryArea
 
      1v84 : Fix device initialisation flags not working when the device number is above 32 (fix #751, #748)
              - this fixes broken SPI when not on standard pins

diff --git a/src/jslex.c b/src/jslex.c
@@ -26,7 +26,7 @@ JslCharPos jslCharPosClone(JslCharPos *pos) {
 
 /// Return the next character (do not move to the next character)
 static ALWAYS_INLINE char jslNextCh(JsLex *lex) {
-  return (char)(lex->it.ptr ? lex->it.ptr[lex->it.charIdx] : 0);
+  return (char)(lex->it.ptr ? READ_FLASH_UINT8(&lex->it.ptr[lex->it.charIdx]) : 0);
 }
 
 /// Move on to the next character

diff --git a/src/jsutils.h b/src/jsutils.h
@@ -56,46 +56,49 @@ extern int isfinite ( double );
 
 #if defined(ESP8266)
 
-// Place constant strings into flash when we can in order to save RAM space. Strings in flash
-// must be accessed with word reads on aligned boundaries, so we'll have to copy them before
-// regular use.
+/** Place constant strings into flash when we can in order to save RAM space. Strings in flash
+    must be accessed with word reads on aligned boundaries, so we'll have to copy them before
+    regular use. */
 #define FLASH_STR(name, x) static char name[] __attribute__((section(".irom.literal"))) __attribute__((aligned(4))) = x
 
-// Get the length of a string in flash
+/// Get the length of a string in flash
 size_t flash_strlen(const char *str);
 
-// Copy a string from flash to RAM
+/// Copy a string from flash to RAM
 char *flash_strncpy(char *dest, const char *source, size_t cap);
 
+/** Read a uint8_t from this pointer, which could be in RAM or Flash.
+    On ESP8266 you have to read flash in 32 bit chunks, so force a 32 bit read
+    and extract just the 8 bits we want */
+#define READ_FLASH_UINT8(ptr) ({ uint32_t __p = (uint32_t)(char*)(ptr); volatile uint32_t __d = *(uint32_t*)(__p & (uint32_t)~3); ((uint8_t*)&__d)[__p & 3]; })
+
+#else
+
+/** Read a uint8_t from this pointer, which could be in RAM or Flash.
+    On ARM this is just a standard read, it's different on ESP8266 */
+#define READ_FLASH_UINT8(ptr) (*(uint8_t*)(ptr))
+
 #endif
 
+
 #if defined(ESP8266)
-// For the esp8266 we need to add CALLED_FROM_INTERRUPT to all functions that may execute at
-// interrupt time so they get loaded into static RAM instead of flash. We define
-// it as a no-op for everyone else. This is identical the ICACHE_RAM_ATTR used elsewhere.
+/** For the esp8266 we need to add CALLED_FROM_INTERRUPT to all functions that may execute at
+    interrupt time so they get loaded into static RAM instead of flash. We define
+    it as a no-op for everyone else. This is identical the ICACHE_RAM_ATTR used elsewhere. */
 #define CALLED_FROM_INTERRUPT __attribute__((section(".iram1.text")))
 #else
 #define CALLED_FROM_INTERRUPT
 #endif
 
-
-
 #if !defined(__USB_TYPE_H) && !defined(CPLUSPLUS) && !defined(__cplusplus) // it is defined in this file too!
 #undef FALSE
 #undef TRUE
 //typedef enum {FALSE = 0, TRUE = !FALSE} bool;
-#define FALSE 0
-#define TRUE 1
+#define FALSE (0)
+#define TRUE (1)
 //typedef unsigned char bool;
-//#define TRUE (1)
-//#define FALSE (0)
 #endif
 
-// Not needed because including stdbool.h instead.
-/*#ifndef Arduino_h
-#define true (1)
-#define false (0)
-#endif*/
 
 #define DBL_MIN 2.2250738585072014e-308
 #define DBL_MAX 1.7976931348623157e+308

diff --git a/src/jsvariterator.h b/src/jsvariterator.h
@@ -56,13 +56,13 @@ static ALWAYS_INLINE JsvStringIterator jsvStringIteratorClone(JsvStringIterator
 /// Gets the current character (or 0)
 static ALWAYS_INLINE char jsvStringIteratorGetChar(JsvStringIterator *it) {
   if (!it->ptr) return 0;
-  return it->ptr[it->charIdx];
+  return READ_FLASH_UINT8(&it->ptr[it->charIdx]);
 }
 
 /// Gets the current (>=0) character (or -1)
 static ALWAYS_INLINE int jsvStringIteratorGetCharOrMinusOne(JsvStringIterator *it) {
   if (!it->ptr) return -1;
-  return (int)(unsigned char)it->ptr[it->charIdx];
+  return (int)(unsigned char)READ_FLASH_UINT8(&it->ptr[it->charIdx]);
 }
 
 /// Do we have a character, or are we at the end?

diff --git a/src/jswrap_io.c b/src/jswrap_io.c
@@ -88,8 +88,10 @@ Write 32 bits of memory at the given location - VERY DANGEROUS!
  */
 
 uint32_t _jswrap_io_peek(JsVarInt addr, int wordSize) {
-  if (wordSize==1) return (uint32_t)*(unsigned char*)(size_t)addr;
-  if (wordSize==2) return (uint32_t)*(unsigned short*)(size_t)addr;
+  if (wordSize==1) return READ_FLASH_UINT8((char*)(size_t)addr);
+  if (wordSize==2) {
+    return READ_FLASH_UINT8((char*)(size_t)addr) | (uint32_t)(READ_FLASH_UINT8((char*)(size_t)(addr+1)) << 8);
+  }
   if (wordSize==4) return (uint32_t)*(unsigned int*)(size_t)addr;
   return 0;
 }