how sha256.lua call C function?

[徐威远]

in sha256.lua, C struct and funcions are declared:

typedef struct SHA256state_st

{

SHA_LONG h[8];

SHA_LONG Nl,Nh;

SHA_LONG data[SHA_LBLOCK];

unsigned int num,md_len;

} SHA256_CTX;

int SHA256_Init(SHA256_CTX *c);

int SHA256_Update(SHA256_CTX *c, const void *data, size_t len);

int SHA256_Final(unsigned char *md, SHA256_CTX *c);

]]

...

function _M.new(self)

local ctx = ffi_new(ctx_ptr_type)

if C.SHA256_Init(ctx) == 0 then

return nil

end

return setmetatable({ _ctx = ctx }, mt)

end

I'm confused how luajit finds the location C funcions definded while no ffi.load() is used.

And how can I call some custom C function in default C namespace like above？

Thank you.

[FQ Liu]

~ % grep "int SHA256_Init" /usr/include/openssl/sha.h -n -A2

150:int SHA256_Init(SHA256_CTX *c);

151-int SHA256_Update(SHA256_CTX *c, const void *data, size_t len);

152-int SHA256_Final(unsigned char *md, SHA256_CTX *c);

Functions like SHA256_Init() is defined in openssl library, and had been loaded.

在 2017年7月17日星期一 UTC+8上午11:59:35，徐威远写道：

[徐威远]

Thanks for your help, I have found the  functions defined in openssl-1.0.2k\crypto\evp\e_aes_cbc_hmac_sha256.c

but I still have no idea when and where openresty load them...

在 2017年7月17日星期一 UTC+8下午1:42:24，FQ Liu写道：

[FQ Liu]

When nginx startup, linked library was automaticly loaded.

在 2017年7月17日星期一 UTC+8下午4:36:23，徐威远写道：