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Correctly handle endianness without reference to host platform #1081

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Dec 22, 2020
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Correctly handle endianness without reference to host platform #1081

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72 changes: 16 additions & 56 deletions src/common.c
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Original file line number Diff line number Diff line change
Expand Up @@ -349,49 +349,32 @@
#define L1_WRITE_BLOCK_SIZE 0x80
#define L0_WRITE_BLOCK_SIZE 0x40


// Endianness
// https://commandcenter.blogspot.com/2012/04/byte-order-fallacy.html
// These functions encode and decode little endian uint16 and uint32 values.

void write_uint32(unsigned char* buf, uint32_t ui) {
if (!is_bigendian()) { // le -> le (don't swap)
buf[0] = ((unsigned char*)&ui)[0];
buf[1] = ((unsigned char*)&ui)[1];
buf[2] = ((unsigned char*)&ui)[2];
buf[3] = ((unsigned char*)&ui)[3];
} else {
buf[0] = ((unsigned char*)&ui)[3];
buf[1] = ((unsigned char*)&ui)[2];
buf[2] = ((unsigned char*)&ui)[1];
buf[3] = ((unsigned char*)&ui)[0];
}
buf[0] = ui;
buf[1] = ui >> 8;
buf[2] = ui >> 16;
buf[3] = ui >> 24;
}

void write_uint16(unsigned char* buf, uint16_t ui) {
if (!is_bigendian()) { // le -> le (don't swap)
buf[0] = ((unsigned char*)&ui)[0];
buf[1] = ((unsigned char*)&ui)[1];
} else {
buf[0] = ((unsigned char*)&ui)[1];
buf[1] = ((unsigned char*)&ui)[0];
}
buf[0] = ui ;
buf[1] = ui >> 8;
}

uint32_t read_uint32(const unsigned char *c, const int pt) {
uint32_t ui;
char *p = (char *)&ui;

if (!is_bigendian()) { // le -> le (don't swap)
p[0] = c[pt + 0];
p[1] = c[pt + 1];
p[2] = c[pt + 2];
p[3] = c[pt + 3];
} else {
p[0] = c[pt + 3];
p[1] = c[pt + 2];
p[2] = c[pt + 1];
p[3] = c[pt + 0];
}
return ((uint32_t)c[pt]) | ((uint32_t)c[pt+1] << 8) | ((uint32_t)c[pt+2] << 16) | ((uint32_t)c[pt+3] << 24) ;
}

return(ui);
uint16_t read_uint16(const unsigned char *c, const int pt) {
return ((uint16_t)c[pt]) | ((uint16_t)c[pt+1] << 8);
}


static uint32_t get_stm32l0_flash_base(stlink_t *sl)
{
switch (sl->chip_id) {
Expand Down Expand Up @@ -1779,30 +1762,7 @@ int stlink_trace_read(stlink_t* sl, uint8_t* buf, size_t size) {

// End of delegates.... Common code below here...

// Endianness
// http://www.ibm.com/developerworks/aix/library/au-endianc/index.html
// const int i = 1;
// #define is_bigendian() ( (*(char*)&i) == 0 )

unsigned int is_bigendian(void) {
static volatile const unsigned int i = 1;
return(*(volatile const char*)&i == 0);
}

uint16_t read_uint16(const unsigned char *c, const int pt) {
uint32_t ui;
char *p = (char *)&ui;

if (!is_bigendian()) { // le -> le (don't swap)
p[0] = c[pt + 0];
p[1] = c[pt + 1];
} else {
p[0] = c[pt + 1];
p[1] = c[pt + 0];
}

return(ui);
}

// same as above with entrypoint.

Expand Down